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8]<OU 160337 




JOHN LOCKE, Treatise of Civil Government and A 
Letter concerning Toleration, edited by Charles 
L. Sherman. 

BENEDICT DE SPINOZA, Writings on Political Philoso- 
phy, edited by A. G. A. Balz. 


(Dc Ente et Essentia) 



"Ad Fratres et Socios.* 7 " - 

Translated from the Latin with 
the Addition of a Preface by 




New York London 



All rights reserved. This book, or parts 
thereof, must not be reproduced in any 
form without permission of the publisher. 



" relations exist in God really; in proof whereof we may 

consider that in relations alone is found something which is 
only in the apprehension. . . . This is not found in any other 
genus; forasmuch as other genera, as quantity and quality, in 
their strict and proper meaning, signify something inherent in a 
subject. But relation in its own proper meaning signifies only 
what relates to another/' 

"Now whatever has an accidental existence in creatures, when 
considered as transferred to God, has a substantial existence/ 5 

Summa Theologica, Qs. 27-49, 




I Biographical Account of St. Thomas Aquinas . . xiii 

II Thomistic Anthropology and Epistemology 

1. Basic Features of Doctrine xvii 

2. The Order of Abstraction and the Order of 

Signification xxiv 

Concerning Being and Essence 
Introduction 3 


I What the Names Being and Essence Commonly Sig- 
nify 4 

II What Essence Is in Composite Substances ... 7 

III How Essence Is Disposed towards Genus and Differ- 

ence 16 

IV By What Mode Essence Exists in Separate Sub- 

stances 21 

V How Diverse Essences Exist in Diverse Things . . 28 

VI How Essence, Genus and Difference Exist in Acci- 
dents 33 





IN RECENT times St. Thomas Aquinas has come to suggest 
problems and solutions which are of the first order of im- 
portance for speculative thought. And I do not mean merely 
for the history of philosophy or for the cloister-like seclusion of 
the class room in mediaeval philosophy. He is something more 
than a mere interval in the creative advance of evolution. First 
principles never become obsolete, and the doctrine of St. 
Thomas is replete with steady and rigorous ideas which can 
accomplish much in clarifying the present confusion of the 
arts and sciences. It is therefore time that he should leave the 
company of Latin scholars with their forbidding array of critical 
apparatus, footnotes, comments upon and citations of compara- 
tive sources, and the dead weight of the gloss which preserves 
the letter but destroys the spirit. 

This translation of the De Ente et Essentia renders into Eng- 
lish a very compact and highly significant matrix of arguments 
concerning the status of essence, being and existence. As a 
preparation for its principal task the opusculum examines the 
character of incomplex terms, genus, species and difference, 
how they stand to each other within the defined whole of an 
essence and in so doing how the incomplex terms are signs 
which signify the nature of individuated and unified substantial 
wholes existing in nature independently of the human mind. 
In addition, when St. Thomas passes from corporeal substances 
as such to "intelligences," man and the angels, an example is 
given of the rhetorical shift by which scholastic thought effected 
the trope from the literal to the figurative. This rhetorical shift 



is in itself a study in the 'superposition' of concepts or iso- 
morphic relationships. Modern formal logic makes the excessive 
claim that it has accomplished the first real advance in logic 
since Aristotle. If indeed it has measurably multiplied the 
modes of predication and relational order which can be grasped 
by voluntary synthetic acts of thought, still it most certainly 
has not clarified the modes of signification (symbolic reference) 
handled so astutely by the scholastics. 

The reader, if he is accustomed to the inorganic and loose 
discursiveness of modern philosophy, nay, at times its almost 
total lack of order and discipline, may find that it requires a 
special act of the will to master the concepts of St. Thomas. 
But if he does master even the brief content of this little 
work he will find himself possessed of what may be called a 
prolegomena to every past and future system of philosophy. 

Nor does the last sentence claim too much. St. Thomas was 
not a mere transitive conductor, namely, a compiler, translator, 
commentator and encyclopedist, an exalted eclectic, careless in 
his sums of addition. He was possessed of a bold and original 
mind capable of effecting a monumental synthesis of principles 
gathered from widely diverse sources. In his works Plato, 
Aristotle, Plotinus, the patristics, Proclus, Porphyry, Boethius, 
St. Augustine, Averroes, Avicenna, and a host of Latin doctors, 
to mention a few, are sifted and cleansed. As a matter of course 
it is true that running through all of his post-Athenian sources 
there is a principle of traditional unity, namely, the "logos 
tradition," however diffused it may become at times, derived 
from Plato and Aristotle. It is also very significant that St. 
Thomas refers to Aristotle as the Philosopher and to Averroes 
as the Commentator. The Summa Theologica then, his crown- 
ing work, is more than a sum of theology. It is the cumulative 
apex of some seventeen centuries of continuous tradition, both 
pagan and Christian, in the service of theological science. 


Theology was in truth the final cause, and though indeed 
philosophy was in subordination to it, still philosophy had an 
autonomy of its own. Logic is the common instrument of phi- 
losophy and natural science, dealing with the natural order of 
substances and leading up to metaphysics or the doctrine of 
being qua being. By a shift in intention the modes of logic 
lead from corporeal substances by analogy to insights concern- 
ing extra-natural entities. Metaphysics or first philosophy deals 
with the transcendental predicates: being and non-being, one 
and many, true and false, good and evil, thing and something, 
examining the order of nature and the order of reason to test 
their accord, namely, the similitude or commensuration of the 
beings of nature to the beings of reason. Logic is the instrument 
for formulating simple and complex modes, the centrum of 
philosophy, and in order for philosophy to be a means to 
theological science logic must be promoted in its own order as 
if it were an end in itself. Philosophy as instrumented through 
logic deals with the natural order and in so doing supplies 
evidence for the confirmation of faith. Indeed it supplies the 
literal terms (grammar) from which rhetorical method ad- 
vances to an understanding of intelligences and finally to an 
analogical though finite and imperfect grasp of God's infinite 

The relation of philosophy to natural science was in essence 
the same in peripatetic scholasticism as it is today. A lack of 
emphasis on the discovery and perfection of mechanical or in- 
strumental material and efficient means need not obscure the 
relationship, since engineering does not exhaust the whole of 
human science* Scholasticism clearly appreciated the fact that 
before science could begin there must be a discipline inde- 
pendent of natural things in terms of which propositions about 
nature can be formulated. Today the pragmatists in their over- 
tures to logical positivism seem inclined to join two estates 


as a result of the recognition that science must possess a gen- 
eral method of procedure in regard to its subject matter, an 
instrument moreover which can be understood in some sense 
at least as a result of voluntary synthetic acts or syntactic opera- 
tions. This is an open concession to the Aristotelian truism that 
it is absurd to seek knowledge and at the same time the means 
for obtaining knowledge. Science consists of propositions about 
natural things, but it must so consist by means of an inde- 
pendent discipline which supplies it with dependable first prin- 
ciples. In addition it must explain the relation of rational modes 
to natural modes and how the former derive their being and 
truth from the latter if it desires to avoid mythology however 
empirical or rational. It is interesting if somewhat disquieting 
to watch the speculative psyche pass through its stages of re- 
capitulation. But I would not imply that the pragmatists have 
advanced to the stage of explaining the relationship of the 
sign to the thing signified. 

The De Ente et Essentia is a complete whole in itself in the 
sense that the axioms, definitions, postulates and initial theorems 
of Euclid constitute a whole. But even so the student may wel- 
come some extrinsic help, since the propositions refer beyond 
themselves to other texts and are referred to from other texts. 
The De Ente is in effect an argument matrix or doctrine 
function for the other Thomistic works. 

I believe that the most valuable assistance which this preface 
can offer is that of explaining and elucidating the principal 
concepts of the text. There are of course alternate routes by 
which such help may be conveyed, as for instance that of his- 
torical and comparative criticism joined to a scrutiny of genetic 
origins. But, again referring to Euclid, I observe that one might 
read all the foot-notes in Sir Thomas Heath's excellent edition, 
gathering thereby a vast quantum of assorted facts. Still it 
suffices to say that the information could have no genuine 


ground for being remembered without a grasp of the dem- 
onstrated order and connection of the propositions. After a 
brief biography of St. Thomas, I propose, therefore, to set my sail 
boldly before the wind of doctrine. I concede, however, that the 
nautical maxim to the effect that even a good wind is an evil 
wind, contains a relevant warning. 


AT ROCCASECCA near the little village of Aquino, towards 
Naples, St. Thomas Aquinas was born circa 1225. His 
family was descended from an illustrious line of noblemen, his 
own father having the rank of count. For those who lend 
credence to signs it must seem strange that the name of his 
birthplace was so inauspicious for one who was to become a 
fountain of scholastic wisdom. 

His early education began with the Benedictine Monks at 
Monte Cassino, but he later went to Naples where among his 
masters were Petrus Martinus and Petrus de Hibernia. From 
Martinus he learned the trivium and from Petrus de Hibernia 
the quadrivium. The trivium and quadrivium made up the pre- 
liminary matriculation of studies by way of preparation for a 
professional vocation: law, theology or medicine. The trivium 
or trivial arts, consisting of grammar, logic and rhetoric, com- 
posed the three modes of discourse by which discursive ex- 
pression is mastered, so that the trivium is primarily instru- 
mental. The quadrivium, or the four ways, is composed of 
geometry, arithmetic (theory of numbers), music and 
astronomy, and may be considered as the natural or literal 
subject matter of the trivium in the divine order of creation. 
It is curious that the expression liberal arts is derived equivocally 


from the Latin word for book and the Latin word for free, so 
that as a consequence the liberal arts are book arts which make 
the human spirit free from the body and its association with 
particular things. 

After having joined the Dominican Order at Naples, St. 
Thomas subsequently set out for the Convent at Cologne 
where he came into contact with Albertus Magnus, his doctrinal 
master. It is fairly well authenticated that to Albertus Magnus, 
St. Thomas owes his vocation to philosophy and his Aristotelian 
initiation. This is not the place to discuss what St. Thomas 
derived from his master in detail. But it is often pointed out 
that Albertus Magnus assembled the material and began the 
foundation of what St. Thomas later erected into a cathedral of 
doctrine. It is true that St. Thomas soon began to substitute 
the method of running paraphrase for the metaphrases of 
Albertus Magnus in commenting on the Aristotelian works. His 
thought is free from glosses and digressions, exact and rigorous, 
finely balanced and directed towards its central object with a 
clear vision and great foresight. The two Summae exhibit a re- 
duction to a few simple modes of all the complex modes of 
argument employed by his predecessors. His mind was pri- 
marily architectonic and constructive, attributes which do much 
to account for the almost miraculous organization of doctrine 
which he accomplished. 

St. Thomas accompanied Albert to Paris in 1245, and thence 
back to Cologne in 1248. In 1252 the general of his order 
called him back to teach at Paris. This is the period of his 
public lectures, first as a bachelor and later as a master. The 
date of his mastership corresponds with that of St. Bonaventura 
in 1257. After a removal from Paris and a residence in Rome 
where he delivered at the papal court the truths which he had 
meditated, he again returned to Paris in 1268. While in Rome 
he came into contact with William of Moerbeke who is known 


as the major translator of the Aristotelian works from the Greek 
to the Latin. It is important that St. Thomas avoids the transla- 
tions of the Arabians and Jews and returns to the original 
sources for information. His work seems to have been pre- 
dominately occupied with the problem of reorganizing the 
liberal arts and in addition the faculty of theology in respect 
to doctrine. This issued from his Aristotelian background. The 
two Summae supply a basis of internal or doctrinal organiza- 
tion which is something other than the organization of the 
physical plant of a university and the building up of a com- 
plex corps of administrative executives. During this period of 
his stay at Paris St. Thomas took a leading part in the serious 
doctrinal controversies being waged there. At all points he 
combated the Averroism of Siger of Brabant, although he re- 
tains such principles of Averroes in his own system as seemed 
to him consistent with Aristotle and the Christian faith. Despite 
the protests of the rector and masters of the faculty of theology 
at Paris, he was again called to Italy in 1272 to organize a 
studium generate, a center of theological studies for a province 
of his order. On his way to Lyons, whither Gregory X had 
called him to assist at the work of a General Council, he died 
in 1274, being then forty-eight years of age. 

In 1323, nearly a century after his birth and a half century 
after his death, Thomas Aquinas was canonized a saint by 
Pope John XXII. Whatever may be the proper statement of the 
grounds of sainthood, his vast intellectual achievements are 
certainly events out of the natural order and appropriate to a 
miracle. His brothers in religion called him 'the angelic doctor'. 

It will doubtless be greatly to the advantage of the reader to 
have a chronological order of the works of St. Thomas, which 
follows, as taken from page twenty of Le Thomisme, par 
fitienne Gilson, troisime Edition, Librairie Philosophique J. 
Vrin, 1927. 

n * * ro 
[later to 1268. 



1. In Boetium de Hebdomadibus (towards 1257-1258). 

2. In Boetium de Trinitate (same date). 

3. In Dionysium de divinis nominibus (towards 1261). 

4. Concerning Aristotle: Physics. 

5. " " Metaphysics 1261-1264. 

6. " " Ethics. 

7. " " De anima. 

8 - ;; ;; e sensu ? sensat -i a ^^ , 

9. De memona et K , . 


10. " " Politics, 

n. " " Second Analytics. 

12. " " De Causis. 

13. " " Meteors 1269-1271. 

14. " " Perihermeneias. 

15. " " De Coelo. 

1 6. " " De generatione et corruptione. 


17. " M In IV lib. Sententiarum ( 1254-1256). 

18. Compendium theologiae ad Reginaldum (1260-1266, or 


19. Summa Theologica. 

Prima pars, 1267-1268. 
Prima secundae, 1269-1270. 
Secunda secundae, 1271-1272. 
Tertia pars, 1272-1273, or 1271-1273. 
Supplementum, by Reginald de Piperno. 

20. Summa contra gentes, 1258-1260, or 1259-1264. 

21. De rationibus fidei contra Saracenos, Graecos et Armenos; 


22. Contra errores Graecorum, 1263. 

23. De emptione et venditione, 1263. 

24. De regimine principium ad regem Cypri. 1265-1266. 

25. De principiis naturae, 1255. 

26. De ente et essentia, 1256. 

27. De occultis operationibus naturae. 1269-1272. 

28. De aeternitate mundi contra murmurantes. 1269-1272. 


29. De imitate intellectus contra Averroistas. 1269-1272. 

30. DC substantiis separatis (after 1260, or about 1272). 

31. De mixtione elementorum. (1273). 

32. De motu cordis. (1273). 

33. De natura verbi intellectus. (Authentic ?). 

34. De intellectu et intelligibili. 

35. Quaestiones quodlibetales. 

Quaest. 7, 9, 10, n, 8. (1263-1268, or 1272-1273). 

Quaest. i to 6, 1269-1272. (Paris). 

36. Quaestiones disputatae. 

De veritate, 1256-1259. 

De potentia, 1259-1263, or 1256-1259. 

De spiritualibus creaturis, 1269. 

De anima, 1269-1270. 

De unione Verbi incarnati, 1268. 

De malo, 1263-1268. 

De virtutibus, 1270-1272, or 1269-1272. 

(Note: See the edition cited for exact arrangement and ex- 



Basic Features of Doctrine 

s a result of his strict adherence to Aristotelianism St. 
Thomas is at infinite pains to clarify and correct the heavy 
charge of Platonism, neo-Platonism and Stoicism in the 
atmosphere of scholastic tradition. The reintroduction of the 
works of Aristotle, translated directly from the Greek, neces- 
sitated a complete reform of philosophy and theology. This 
reconstruction was primarily based on a re-clarification of logic, 
since logic expresses reflexively the structure of modes of know- 
ing. The Angelic Doctor's clarity of intellect was greatly 

xviii PREFACE 

enhanced by this attention to logic, allowing him to direct his 
energy immediately upon the architectonic reform of doctrine. 
Mythological cosmology, the "royal lies" of Plato, were to be 
measured by a program for scientific knowledge the basic 
propositions of which could be about things of nature. 

Theology studies the supernatural order of existence as re- 
vealed in the word of God, whereas philosophy examines the 
natural order as comprehended by reason. Reason demonstrates 
the grounds of credibility for faith, and does so by adducing 
evidence from the natural order. Thus it moves from the better 
known to the less known. In the genetic order of knowing, the 
better known passes from natures to sensible species to uni- 
versals, whereas in the order of intellect there is a reverse 
movement from universals to sensible species to natures. The 
former is the order of abstraction, the latter the order of 
signification. This implies that knowing begins with the con- 
crete substantial unity, or thing, and advances in the order of 
abstraction by a series of steps to a grasp of those entities 
which are univocal signs of one in many, namely, universals. 
Beyond these it infers to simple substances constituted of 
essence and existence rather than of matter and form like con- 
crete entities. There is a continuous order of grades of being, 
each grade possessing its proper operation and hence its proper 
difference and perfection, from natural entities, through quasi- 
material entities (man), to immaterial entities (angels), to 
God as pure act, one and unique. 

Such a graded ordination entails an order of knowing in 
which by shifts from one mode of apprehension to another the 
intellect passes from the literal to the figurative by analogy, 
namely, from modes of signation, to modes of attribution, to 
modes of proportion. The modes of the figurative are super- 
imposed upon the literal by isomorphic relationships or 


analogies of structure in which the literal determinants are 
dropped, i.e. by an increasing remotion of attributes. 

To the extent that the sciences cut off some special aspect 
of nature and examine its properties by abstraction in order to 
formulate propositions about the natural entities, the Thomistic 
program for knowledge is not out of harmony with the 
methods of modern science. For St. Thomas, however, a nature 
is a substance primarily and only secondarily a qualified thing, 
as for instance quantity is its first accident but not commen- 
surately equivalent to substance. The synthetic interpretation 
rests throughout on analysis. Logic is the instrument which 
works with analytic forms, modes of composition and division, 
and thus exploits the structural forms by means of which 
propositions are about the things of nature. But science has an 
analytic remotion, or formal distance, from individuated 
natures, seeing that science deals with the universal which is 
always true or at least true for the most part. 1 From this it is 
to be understood that the terms which enter into propositions 
of science must be univocal signs of many, namely, universals 
abstracted from all contingent increments, so that the abstracted 
quiddity or whatness of the thing is grasped by way of a mode 
of rational being expressive of the essential or necessary features 
of the thing of nature. For St. Thomas philosophy passes 
through science to God, whereas modern science simply passes 
beyond the fact to the proposition about the fact, and worships, 
if at all, efficiency. 

Where the adherents of St. Augustine, namely, the Platonists 
generically, discovered innate ideas and infused illumination, 
St. Thomas posited an a posteriori program for grades of con- 
tinuous abstraction whereby not absolute but only relative 
knowledge is possible. His neglect of the ontological proof of 

1 St. Thomas Aquinas, In II x. DC Anima, 12. "Scientia non cst par- 
ticularium, singularium, corruptibilium." 


God's existence in favor of a posteriori arguments taken from 
principles of Aristotelian physics sums up his rejection of the 
a priori. Moreover the multiplicity of the natural order can only 
be drawn from that order and not from rational psychology 
as an independent moment of intellectual intuition. The divine 
light exists indeed in a remote sense, though not as ideas 
immediately instrumental in analytic thought. Man's active in- 
tellect, operating according to the conditions of abstraction, is 
sufficient to explain how the intellect knows. 

The basis of formal certitude rests in the reflexive act of the 
soul, the 'reflection of the intellect on its own act/ It is on this 
level and through this mode that the intellect grounds the 
syntax of logic respecting both complex and incomplex modes 
of reason. Logic is a discipline dealing with rational entities 
knowable apart from things of nature, and hence the logician 
does not have to know all sciences before he can formulate the 
modes of logic. Logic asserts forms of discourse, but the natural 
sciences use the forms to make assertions about things existing 
in the natural order. Accordingly, the logician unversed in 
biology, for example, will not know the natural entities of 
biology, yet he will know the incomplex and complex dis- 
cursive modes by means of which things biological are for- 

This presents two aspects: i. The reflexive analysis of modes 
of thought, and 2. Natural entities existing independently of 
the knowing intellect. God did not create man and leave man 
to create the inferior beings in the order of creation. Logic is 
then presupposed for science, but in addition the propositions of 
natural science are about univocal signs of many. This latter 
relationship must be conditioned by the thing if there is to be 
an adequation between the sign and the thing signaled based 
on some other principle than the power of the mind to for- 
mulate arbitrary associations. 


St. Thomas agrees with Aristotle that it is absurd to seek 
knowledge and simultaneously the means for obtaining knowl- 
edge. 2 But now it is a basic postulate in Aristotelian analysis 
that propositions break up into their terms. Such terms are 
not logical atoms without intentional structure, but signs which 
signify substances and thus such signs belong to the level of 
intentions or modes of signification. It is then the right, good 
and noble thing that the De Ente et Essentia should invoke the 
investigation of being and essence by reference to intention. 
Modes of signification have a similitude or formal analogy to 
the modes of being in natures, and the intellect is said to 
know, that is, to understand the thing when it has abstracted 
the similitude of its being inasmuch as it is a substantial unity. 

Logic deals with entia rationis, beings of the conceptual order. 
But the res naturae, the thing as individuated, is independent 
of the rational order. Essence exists one way in things, but in 
another way in the mind. Rational essence is composed of signs 
which stand to the thing signaled (the nature), and hence 
the rational essence is by composition and division, but the 
nature of the thing exists as indi visibly individuated. The divis- 
ibility and separation is in the order of abstraction or analysis 
and not literally in the thing in this mode. When one measures, 
for example, a table he does not divide and compose the table, 
but the act of analysis runs thus: a unit (imposed) of the table 
is to its total length as one is to (say) twelve. 8 The predicables 

2 Aristotle, Metaphysics, i, 995 a 12. 
St. Thomas Aquinas, In II Met., i. 5. 

3 A few Aristotelian sources may be helpful: In regard to unified wholes: 
". . . those which are so (scil. wholes) by nature are wholes in a higher 
degree than those which are so by art (scil. fabrication), as we said in 
the case of unity also, wholeness being in fact a sort of oneness." Met. 
1023 b 33 "Now most things are called one because they either do or 
have or suffer or are related to something else that is one, but the 
things that are primarily called one are those whose substance is one, 
and one either in continuity or in form or in definition. . . . While in a 


arc modes for composing and dividing essence, which represent 
significatively the finite or limited whole or the thing of nature. 
Thus an essence is like a set of ratios, or proportion, for the 
signs refer to each other and in addition to that which is 
signaled. It is clear that in the rational order signification 
possesses an analytic remotion or formal distance from that 
which is signified. 

Let, therefore, two orders of reference be posed: i. The 
horizontal order of reference according to which entia rationis, 
beings of the conceptual order, refer to each other. These are 
second intentions in the order of signification and consist of the 

sense we call anything one if it is a quantity and continuous, in a sense 
we do not unless it is a whole, i. e. unless it has unity of form." Met. 
1016 b 7. In regard to the analytic separability of the essence: "...and 
the physicist is concerned only with things whose forms are separable 
indeed, but do not exist apart from matter. . . . The mode of existence 
and essence of the separable it is the business of the primary type of 
philosophy to define." Physics, 194 b 12. "The underlying nature is an 
object of scientific knowledge by an analogy." Physics, 191 a 8. "...and 
when I speak of substance without matter I mean essence." 1032 b 14. 
"It is obvious then, . . . what sensible substance is and how it exists 
one kind of it as matter, another as form or actuality, while the third 
kind is that which is composed of these two." 1043 a 26. "...for in 
everything the essence is identical with the ground of its being." De 
Anima, 415 b 12. "...form or essence, which is that precisely in virtue 
of which a thing is called a 'this'..." De Anima, 412 a 8. In regard to 
essence, nature and substance: "From what has been said, then, it is plain 
that nature in the primary and strict sense is the essence of things which 
have in themselves, as such, a source of movement; for the matter is 
called the nature because it is qualified to receive this, and processes of 
becoming and growing are called nature because they are movements pro- 
ceeding from this." Met. 1015 a 13. "The kinds of essential being are 
precisely those that are indicated by the figures of predication (soil, the 
categories); for the senses of 'being' are just as many as these figures." 
Met. 1017 a 23. "Therefore there is an essence only of those things whose 
formula is a definition." Met 1030 a 6. See further Met. Z. "It follows 
then, that 'substance' has two senses: (A) the ultimate substratum, which 
is no longer predicated of anything else, and (B) that which, being a 
'this* is also separable. . . ." Met. 1017 b 23. Oxford University Press Ed. 

PREFACE xxiii 

predicables: genus, species, difference, property, and accident. 
As such they are terms of discourse. In combination these make 
up a network of rationality by which entia naturae, beings of 
nature, are caught and expressed in the order of universals as 
univocal signs of many. Logic, strictly speaking, is the abstrac- 
tion and reflexive scrutiny of these modes of signification or 
terms of discourse. The second intention is the formal counter- 
part or analogue of a nature, an analytic composite which sup- 
plies the focus of analysis for synthetic natures. It is that by 
virtue of which what is known (the nature) is known. 2. In 
addition to the horizontal reference there is a vertical reference 
to the first intention which is an act of the mind signifying 
things themselves which are not signs of other things. Science 
deals with first intentions, but logic deals with second in- 
tentions. Herein lies the problem of the adequation or corn- 
mensuration of the intellect to the thing. 

Platonism is content to know the order of entia rationis, 
beings of the conceptual order, the ratios and sets of ratios, of 
formal reference in the horizontal plane. How these refer to 
entia naturae f beings of nature, namely, the individuated or 
terminated substance in nature remains a mystery. Platonism, 
then, stops short of the concrete universal or principle and is 
content to exploit the formal connectives of discourse at the 
expense of the terms connected. The Pythagorean reification of 
numbers, namely, that numbers are things, persists in the tradi- 
tion. Hence it is that Platonism studies mind as efficient cause 
primarily expressed in formal intuitions which furnish the ele- 
ments of structural forms. But the individuating cause in nature 
it fails to render intelligible. That anything is received into 
another thing according to the mode of the recipient remains in- 
explicable, but in Aristotelian abstraction the mode of the 
recipient is the crux of the doctrine. 

Abstraction explains the mode of recipiency in the order of 


knowing, since indeed this mode in the abstractive order is the 
analogue of the mode of recipiency in the natural order. The 
passage from matter and form to potency and act is by way of 
analogy, but it should be noted that although all cases of matter 
and form are cases of potency and act not all cases of potency 
and act are cases of matter and form. In addition it is by the 
mode of recipiency in the order of abstraction that the thing is 
continuous with the sensible species and the sensible species 
with the intelligible species. 4 But this remains to be explained 
in the following section. 

The Order of Abstraction and the Order of Signification 

To refer to man as a little higher than the brutes and a little 
lower than the angels is a familiar figure of literature, and 
implies that man has a relative position in the order of creation 
which is somehow measurable. Perhaps it is from this source 
that the term value in ethics originated, for values are cer- 
tainly assignable to functions of measurement. At any rate the 
figure of speech may be unequivocally traced to the scholastic 
scheme of anthropology wherein man's good is intimately asso- 
ciated with his created mode of being in the continuity of the 
divine order. It is a principle of scholasticism that each creature 

4 "The 'originative sources', then, of the things which come-to-be are 
equal in number to, and identical in kind with, those in the sphere of 
the eternal and primary things. For there is one in the sense of 'matter', 
and a second in the sense of 'form': and, in addition, the third 'origina- 
tive source* must be present as well. For the two first are not sufficient to 
bring things into being, any more than they are adequate to account for 
the primary things/' "But the third 'originative source' must be present 
as well the cause vaguely dreamed of by all our predecessors, definitely 
stated by none of them." Aristotle, De Gen. et Corrup., 335 a 27 and 
335 b 8. Oxford University Press Ed. 


exists by its proper or differentiating act which is also its proper 
measure of perfection as derived from God, the First and 
Pure Act. There is then a continuous order of creation from 
God, the First Act and Origin, through the hierarchy of 
angels, through man, animals, and vegetables to things in- 

The human soul which is last in the order of intelligences 
is first in the order of material forms. It is differentiated from 
corporeal bodies qua corporeal by its proper act, namely, the 
mode of knowing which results from its assigned measure of 
being or perfection. Inanimate things in their own order re- 
ceive their act from a principle exterior to them, whereas 
though the soul is in an order of being received from God it 
has yet an intrinsic principle of operation. It belongs to the 
order of the living or animate which moves itself by a proper 
economy of operations intrinsic to itself. On the other hand the 
forms of elements which are at the greatest distance from the 
divine act and in the greatest propinquity to matter have no 
operations which exceed active and passive capacities, such as 
rarefaction and condensation, etc. simple dispositions of 
matter. Quantity, or the relative expansiveness of a body, is a 
fundamental attribute, the first accident, of corporeal sub- 
stances. It is a function of primary matter, as the reduction of 
its multiple elements to substantial unity is a function of its 
limiting or finite form as actuated in its operation. 

Elements are ordered to each other according to act and 
potency, and indeed actuality and potentiality are present in all 
the categories, but not apart from the manner in which the 
categories are accidents of substance. A mere aggregate or col- 
lection of elements cannot be so compounded as to form a real 
unity unless the elements be so necessarily ordered to each other 
as to possess unity in potency before it is possessed in act. It 


follows, therefore, that causes essentially ordered are causes 
hierarchically and necessarily ordered, so that if discontinuity of 
being is apparent there is nevertheless continuity of order. Ac- 
cordingly, elements, whether simple or complex, which can 
combine so as to constitute a substantial unity do so through 
a necessary disposition which they have to each other, namely, 
the determinable capacity of one to receive the determinate and 
hence determining act of the other. 

The act of anything to the potency of something can be 
understood, as indeed conceived by Aristotle and following him 
St. Thomas, as the order of a continuous proportion, the ratios 
of which are terminated in the correlatives of act and potency 
as in anything to something. Things which differ and yet are 
disposed as act to potency are mediated into one thing by the 
assimilation of the act to the potency. If one thing is con- 
tinuous with another the inner bounds have yet a term in com- 
mon, as for instance in this continuous proportion: 2:4:14:8 
:: 8 : 16 :: etc. . . . 

The order of continuous proportion is the analogical prin- 
ciple according to which God distributes His justice, or merits 
and awards. But the essence or nature of each created thing, 
that is, the delimited and limiting mode of its production, is 
the proper act of creation assigned to the thing causing it to 
be what it is and differentiating it as a such from other modes. 
Accordingly, an immediately superior thing in the continuous 
order of creation has yet a term in common with its imme- 
diately inferior thing, and by this they stand to each other as a 
conatus of act and potency. It must be remembered, however, 
that if two such things have a term in common and are alike 
in a certain respect they yet are unlike in a certain other 
respect according to the proper act of each. Thus the proper 
act of a corporeal body qua corporeal is to be such a relative 
multiple of three dimensions, while the proper act of an 

PREFACE xxvii 

animate body is to be alive, and of an intelligence to be in- 
tellective so that one perfection is united to another. 

From what has been said an introduction is given to the 
meaning of the principle that anything is received into another 
according to the mode of the recipient. And by the continuous 
proportion of any two things to each other as limited by form, 
terminated by matter and actualized by an efficient cause, an 
operation as proper or contingent, it can be seen what act and 
potency are. Things which are in immediate ratio as continuous 
proportion are said to be connatural with each other, and this is 
the basis upon which a substance has one perfection and in 
addition another perfection. If the problem of duality is of 
moment it should be observed how it is present in one mode 
but not in another, because the duality of two terms is as act to 
potency as one middle term in a continuous proportion is to the 
other. Hence there is not a duality of two independent sub- 
stances in the Cartesian manner, as of mind and extension, 
but a duality of interdependent terms within the continuity of 
operation. The grade of a created being is measured by the 
simplicity or diversity of its powers of operation inasmuch as 
these are actualized. One created being is superior to another, 
and hence excels or is more noble, in the measure in which its 
powers of operation are simpler, that is, approach reduction 
to a power one and numerically the same. It appears, therefore, 
that according to man's finite vision classification cuts across 
the continuity of God's creative act according to the diversity 
or simplicity of powers by which a thing has its act. In Aristotle 
is contained the concept of autonomy which is notwithstanding 
in subordination, a principle so important to St. Thomas in 
refuting pantheistic influences in scholastic theology. The nature 
of a thing is the first principle of its operation for the per- 
formance of which the thing has come into being, or in general 
the operation which anything is adapted to perform. But 

xxviii PREFACE 

essence is that by virtue of which a thing is what it is neces- 
sarily and primarily as intelligible, or in general that in virtue 
of which it is constituted in a determinate degree of primarily 
intelligible being. The one stands to the other as the links of a 

Now that man has been given a situs in the network of 
creation it is possible to examine him as a substance composited 
of matter and form and yet constituting a substantial unity. 
This can best be conducted by an analysis of the order of ab- 
straction in the process of coming to know. 

The soul is the actuality of an organic body possessing the 
power of life, wherein it is to be understood that the body is 
a corporeal substance as an organic unity or whole consisting 
of an organization of parts or functions. Life is the power of 
self-movement exercised by virtue of itself, yet only inasmuch as 
an organic body is such a grade of being in the divine order of 
creation. To be alive and to be an organization of functions 
by virtue of the act of living is the proper operation of an 
organic body. 

As the body alone is not a substance so also the soul alone is 
not a substance, for the animated body is not an accretion but 
a concretion, being a composite of matter and form unified by 
its proper operation. Because of this the separation of soul and 
body is to be understood in two modes: i. Literally, as the cor- 
ruption of a corporeal body to which the soul is; 2. Figuratively, 
as a mode of diction, in that by analysis the soul is distinguished 
from the body. 

An organic body possesses potentialities which are both active 
and passive. The actuality of an active power is an activity or 
an efficient cause per se operable, whereas the actuality of a 
passive power is the condition of change by an extrinsic agent. 
Active potency is a power to operate, but, on the contrary, 
passive potency is a power to receive; and potency is relative 


to the act and for the sake of the act. Moreover a passive 
potency is not a non-active potency, but a potency which is 
passive before being operative, namely, one that must be in- 
formed by something other than itself before being in act. A 
passive potency is a mean term in a segment of change, as for 
instance the term b in the proportion a : b :: b : c; for act and 
potency being continuous must have a term in common and 
yet a difference. From what has been said it follows that every 
body has a constitutive principle by virtue of which it is that 
which it is and performs that which it performs. This is its 
proper perfection, since each creature exists by its proper act and 
perfection. Accordingly, an actual organic body is a corporeal 
substance, the organized parts of which are its matter, pos- 
sessing powers, and the soul of which is the form, the actuality 
of the aforesaid powers. 

The soul as such is the actuality of both the passive and 
active powers of the organic body. It is a principle of cognition 
that powers are known from their acts as the potentialities of 
a substance are known from its operations. In respect to the 
soul the suppositum or subject of operation is the composite 
of body and soul, that is to say, the primary and efficient act by 
virtue of which soul and body constitute a substantial unity 
rather than an accidental association. The whole man in action 
is the subject of analysis as opposed to any restricted aspect of 

A vegetative soul consists in the reduction of the operations 
of nutrition, growth and reproduction to unity. An animal, 
being one grade removed in excellence, has a soul which is a 
unity of the vegetative operations and in addition that other 
perfection which supervenes to it, namely, the operations of 
sensation, locomotion and appetite or desire (the affective 
impulses). The soul of a man is a reduction to unity of the 
vegetative and sensitive operations and another perfection 


which supervenes to him and is the operation of intellect. It is 
a basic principle that one nature possesses a greater perfection 
over another according to its greater simplicity of operation, 
that is, according to the measure in which it reduces manifold 
operations to a few unified operations. Simultaneously, this 
is its mode of being and good or measure of excellence (ex- 
celling) in the created order of substances. Man actualizes his 
perfections in the measure in which he actualizes his proper 
powers, but especially the operation of intellection. It is this 
operation which constitutes his proper difference and sets 
him apart in the genus animal. 

In the order of becoming human powers are compendent 
thus: vegetative, sensitive, appetitive, locomotive, and intel- 
lective. Man vegetates, desires (seeks or avoids), moves and 
understands. Sense depends on vegetation, intellect upon sense, 
and desire upon either sense or intellect. Man seeks or avoids 
images and ideas. But the proper act of intellect consists in 
seeking ideas, namely, universals. Motions follow as an ex- 
ploitation of what is desired. 

The powers of man as man issue from his substance as acci- 
dents of his nature. Sense is a passive power and that by which 
man is in potency to sensibles, since sensible things are the 
agents of this power and related to it as the efficient cause of 
its becoming actual. Sensible things, corporeal substances or 
natures outside of the body, are in act apart from the senses. 
Thus it is that sensible things in act possess an active agency 
with respect to the senses, seeing that they are potentially effi- 
cient causes of sensation. The passive potency or recipiency of 
the senses is brought into act by virtue of the operations of 

The sensible in act is identical with the sense in act in the 
manner that b is a common term in the proportion a : b :: b : c. 
Since the passive matter of the sense organ can be differentiated 


by the active agency of the sensible thing, the sense organ is 
the material cause of sensation, for that which can be differ- 
entiated is matter or like matter. Sensation is the actualization 
of this passive potency, consequently it follows that the sensible 
nature as actually sensed is one and the same with the sense 
actualized by assimilation. 

In general the senses are all things as sensed since they are 
in potentiality to all sensible things. But it should be observed 
that although the senses are assimilated to the sensible thing as 
actual, still the distinction must be made that the sensation, 
being the actualized sensible in the actualized sense, is some- 
thing other than the matter of the sensible nature. Sensations 
are entia sensus, beings of sense, or entia sensus et imagi- 
nationis, beings of sense and imagination. The sensory simili- 
tude (phantasm) is abstracted from the matter of the sensible 
thing, but it is still expressive of the material conditions of the 
sensible thing as individuated in this or that nature although 
it is received according to the mode of the recipient. Since the 
subject of sensitive knowledge is always a singular, an in- 
dividuated nature extra mentem, namely, a corporeal substance, 
corporeal substances belong to the literal order of independent 
existences so that sensitive knowledge gives the ground of the 
first intention. This is the first figure of remotion, when the 
order of signation is taken as the reverse of the order of ab- 
straction, and stands for the thing under its first abstraction 
and yet as it is immediately in its individuation. 

Sensations stand for natural things immediately as actualized 
in sense, that is to say, the bringing into act of the potency of 
the sense. The senses, however, are not reflexive and do not 
know themselves as powers or acts. In the reverse order of 
signation, the sensation is not that which is known but that by 
means of which the sensible is known. What is known of 
an individual corporeal thing is its individuated nature sepa- 

xxxii PREFACE 

rated from the matter of the substance, but retaining the con- 
ditions of individuality. Accordingly, the sensation is not sig- 
nificant as a physiological event but as a potential sign. 

The intellect is both an active and a passive power. Of these 
the passive or possible intellect is in potentiality to all intelli- 
gible things, and the active intellect is the efficient cause of the 
transmission into actuality of the potencies of the passive in- 
tellect. It is the passive intellect which is in potentiality to all 
sensible species, but things are not actually intelligible apart 
from the act of intellection. For example, corporeal substances 
are actually sensible but only potentially intelligible, so that 
they are actually intelligible only as actually understood. Con- 
sequently, it follows that intelligible things are not the efficient 
cause of the actualization of the passive intellect. Since, as 
Aristotle asserts in the DC Anima and following him St. 
Thomas, the object of knowing and the act of knowing are one 
and the same, the intelligible in act is the intellect in act. The 
actualization of the potential intelligibility of a thing is the 
same as the actualization of the passive intellect. It should be 
understood that the actual intellect is whatever it actually 

Although the intelligible thing in potency is different from 
the passive intellect in potency, nevertheless as actualized they 
are assimilated. The first operation of the active intellect is ab- 
straction, and abstraction is the primary reduction of the passive 
intellect from potentiality to act, or in general the reduction 
of potentially intelligible things to things understood. 

Material things, as has been said, are actually sensible but not 
actually intelligible, inasmuch as their forms are individuated 
by material ingredients. Only by abstraction are they actually 
intelligible, and it may be said that things are actually intelli- 
gible in the measure in which they are abstracted from matter. 
Abstraction is the power of the active intellect to exclude in- 

PREFACE xxxiil 

dividuating conditions. But so far as the matter of knowledge 
is concerned intellect is absolutely dependent upon the senses. 
Natures exist as modes of accidents in corporeal substances, 
whereas essences exist as the modes of accident in the intellect; 
but as has been seen, essence is continuously conditioned by the 
nature so that the essence as abstracted is what the thing is in 
its proper and necessary mode apart from all contingent in- 
crements. The thing is that which is understood by means of 
the essence. 

Essences, being entia rationis or beings of reason, are that by 
virtue of which the intellect understands natures inasmuch as 
they are natures, namely, as such a necessary being freed from 
all improper accidents. Sensitive knowledge is the material 
cause of intellective knowledge and leads to the quiddity of the 
thing, that is, the formal equivalent of the thing according as 
it is that kind of thing and not another. 

The order of signification is the converse of the order of 
abstraction, but presupposes it. Abstraction is ordered thus: 
knowledge of singulars by sense precedes knowledge of the 
universal by intellect. First genera are abstracted and then 
species. Species are differentiated by a distinction of proper 
operation in the thing, just as animal is vital but man is 
rational. The genus is to the species as matter is to the form, 
since the species are differentiated from the genus by a proper 
distinction of act. 

Whereas the senses are not reflexive, not knowing their own 
acts, the intellect is reflexive and does know its own acts, powers 
and abstractions. The intellect knows that it is a substance 
through its accidents, and furthermore it knows what it is 
actually by the condition that the object of thought and the 
act of thought are one and the same. Hence it is that the 
intellect infers from its accidents to its substance. The concepts 
of logic are abstractions from entia rationis, beings of reason, 

xxxiv PREFACE 

as such, whereas the concepts of metaphysics are abstractions 
from common intelligible matter and regulate the accord of 
concepts of reason to the modes of things according as being, 
one, true and good are present to the thing and the essence. 
Logic is a means between nature and metaphysics and only 
when so understood does it preserve its proper limitation and 

Nature is an order of individuated things in which such 
things come to be and perish by a multiplication of formal 
act in matter consistent with the principle of one and many 
in material process. Substances are in nature simpliciter. But 
man in his finite and discursive capacity knows by virtue of 
analysis and only reaches synthesis after laborious efforts and 
even then only imperfectly. Man must know by division and 
composition or specially conditioned qualifying operations. The 
order of knowing is grounded in the order of existence through 
the continuity of abstraction, though the intellect must under- 
stand by means of its reflexive powers. 

The categories deal with the advention of accidents in sub- 
stance, corporeal substances which are delimited and hence 
limiting wholes. Hermann Weyl observes on page one, 30, of 
his Philosophic der Mathemati^ und Wissenschajt: "Auch die 
Aristotelische Logik war im wesentlichen abstrahiert aus der 
Mathematik"; and he might have observed that a natural sub- 
stance is like a finite magnitude or whole, though not neces- 
sarily quantitative as such. Genus, species, difference, property, 
and accident, the predicables, are fabrications of the intellect, 
but as analytic similitudes or analogues of substance they in- 
dicate discursively the necessary mode of a substance or the 
relative limitation of categoric accidents. A limited whole in the 
order of nature can be brought into commensuration with a 
limited whole in the order of reason, and thus Aristotle, and 
after him St. Thomas, affirm that nature divides readily into 


genera and species. The nature is that which is known, whereas 
the essence is that by virtue of which it is known. 

Matter is to form as genus is to species, from which it is 
to be understood that as matter is that which is differentiated 
by formal act in the natural order, so genus is that which is 
differentiated by the intellective act in the rational order. And 
indeed it is important that the analytic remotion entailed should 
be guarded and preserved if a confusion of domains of reference 
is to be avoided. Species are explicitly differentiated by the 
active intellect assigning the proper act of the thing consti- 
tuting the species as such a kind. This it does respecting the 
sensible species actualized in the senses by the active agency of 
the thing. Specific unity expresses the formal similitude of a 
universal as an univocal sign of many as referred from a sec- 
ondary substance (analytic order of reason) to multiple pri- 
mary substances (order of independent natures) which are in- 
dividuals of a like species. Since the delimiting and hence 
limiting act of the primary substance determines it to be what 
it is, the form is in its way the cause of specific unity. Nu- 
merical unity expresses the discrete oneness of the multiple 
individuals constituted according to similar specific acts. It thus 
expresses the generality of distinction and the material multi- 
plicity of primary substances having the same secondary sub- 
stance. It should be carefully noted that numerical unity, far 
from excluding specific unity, presupposes it actualized in the 
individual in the sense that the unity or indivision of the nature 
(primary operation by virtue of which a thing is what it is), 
the principle of specific unity, is of necessity antecedent to a 
substance being numerically one. The universal is a common 
sign of many, but it is such through the similarity of the act 
by which each of the many have specific unity as a precondition 
of their oneness with respect to multiplicity. Nor does the 
universal which refers to natures have an existence over and 

xxxvi PREFACE 

beyond the natures as the Platonists are accustomed to con- 

Matter is the principle of the many in the order of natures 
or primary substances, seeing that it is the principle according 
to which the proper specific act is multiplied into a multiplicity 
of individuals after the kind of the species. Genus, then, is the 
first qualification of substance as a something potential to 
differentiation, whereas species issue from the first actuality 
of difference by means of the proper operation. The similitude 
of the differentiating act in a certain multiplicity of natures is 
the ground of genus, while the differentiating operation itself 
as actualized is the ground of the specific individual. Multiple 
units are the natural sum of individuated natures, and thus the 
statement that universals are univocal signs of many is to be 
understood as a cross reference of signs in the universal mode, 
since the universal expresses unity and community. The soul 
abstracts the intention from many particulars and apprehends 
that they bear a ratio of similitude to one another in respect of 
act, but it apprehends in addition that they are one and discrete 
because the specific act of the being of each renders each a one 
numerically distinct from the others. It should be observed, 
however, that the universal is not based on an enumeration 
since one instance suffices for the apprehension of the proper 
act by which the nature is necessarily what it is. "It appears 
that it is universal according to act properly speaking, since 
an intention is abstracted from many, considered as one and the 
same in principle by means of judgment according as it is 
abstracted from many, yet plurified according to the being 
which it has in them.'* 5 What the metaphysician discusses in 
terms of the potentiality and actuality of the thing the logician 
formulates as an intention. 

An accidental accident as opposed to a proper accident is an 
5 DC Univertalibus, attributed to St. Thomas Aquinas. 

PREFACE xxxvii 

increment which may or may not accrue in addition to the 
proper accident of a substance. It is derived from the material 
or contingent aspect of the matter as a margin of potency. A 
property, however, is a sort of secondary proper act, just as in 
man the property of risibility is an act issuing from an appre- 
hension within the intellect. Whereas properties issue from the 
proper accidents, contingent accidents do not. Contingent acci- 
dents may form descriptions, but they cannot signify what a 
thing is primarily as a nature or mode of substantial unity of 
this or that grade of perfection. 

The first intention is a sensation actualized in the potency 
of sense by the active agency of the sensible body; consequently, 
it is a sensible substitute of the thing, but to be understood as 
the substitute of the thing as it is and not as a sign referring 
to other things. As such it is a potential sign in the order of 
abstraction. Such intentions are the implicit subject matter of 
natural science. The second intention, or that by virtue of 
which what is known is known, is the analogue of the first 
intention as it is rendered intelligible by the intellect in act, 
and thus as existing as the essence of the sensible thing freed 
from all contingent increments of individuation. Further, it is 
the thing as ultimately analyzed by reflexive intellective acts 
whereby what is generically implicit in first intentions, and 
hence in like things, becomes discursively explicit, namely, 
according to signation by genus, species, difference, property 
and accident. 

Since the intellected essence expresses the necessary mode of 
being whereby the thing must be what it is, and hence dis- 
tinguishes the basis of generic similitude through specific act, 
individual difference (the basis of numerical multiplication of 
the individuals in quantified matter after the kind of a species) 
must ensue from a condition in addition to the essential mode 
of being. This condition ensues from accidents which advene 

xxxviii PREFACE 

to the nature of the thing in a marginal aspect, but these acci- 
dents are not necessary acts of the natural thing, that is to say, 
not that by virtue of which the thing is formally what it is, 
and hence they do not ensue from the specific operation as such. 
Materia signata (or a determinacy ensuing from a grade of 
being in matter, which a given substance has prior to the 
supervention of a further perfection) is the basis of numerical 
distinctions. It follows from this that though the specific unity 
of the individual makes it numerically one as such a kind of 
species, still individuals differ from each other as things of the 
same species by accidental factors derived from matter and not 
from the proper form. These signaled material factors are in- 
crements outside of the formal operation by virtue of which a 
nature primarily exists and is intelligible. It may be said that 
although the thing is and is intelligible essentially by virtue of 
its proper operation, still matter as determined by active and 
passive qualities, such as rarefaction and condensation (simple 
dispositions of matter in excess of pure potentiality in the order 
of substance), has a certain determined character prior to the 
supervention of another perfection. Hence it is that the dis- 
tinctions of materia signata ensue from material dispositions 
and not from essential form or proper act. An inferior mode of 
being stands as matter to a superior mode of being, and can be 
assimilated to the superior whereby it individuates the superior 
mode. It is for this reason among others that there is not one 
common or generic soul of all men, but each man has an in- 
dividual soul peculiar to himself. 

But the individual is not another predicable as some thought, 
for this would be an equivocation between the natural order 
and the rational order. The first intention is the singular sign 
of the sensible thing as assimilated in sense, and therefore of 
the individuated thing; consequently, it is the potential sign 
by virtue of which the nature (that which exists) is known, 

PREFACE xxxix 

but it is actually so known as a second intention in the active 
intellect and thus as freed from all improper accidents. The 
second intention is that by virtue of which the thing (that 
which exists) is known in its primary actuality, and hence as 
a necessary mode of essence. 

The categories deal with inherence on the basis of substance 
as the primary mode of being. They relate to qualified aspects 
of natures and are analytically formulable by means of the 
delimiting predicables as modes of substantial being. It should 
be observed that although there are as many kinds of being as 
there are kinds of predicaments (categories), yet all the sec- 
ondary categories reduce their qualifications to substance. Sub- 
stance is not a mode of inherence, but if it sometimes seems so 
it is according to the manner in which second intentions (sec- 
ondary substances) stand to first intentions which are assimi- 
lated from natures by the senses. Thus it is that genus is to 
species as matter is to form, since informed matter is the 
divisible in nature, wheras informed genus is that which is 
divisible in thought. 

Relations or the order of one thing to another express the 
mode in which act stands to potency as correlative opposites, 
and hence the order in which one thing is assimilated to an- 
other. It has been suggested by the figure of continuous propor- 
tion that in its necessary aspect this represents a compendent 
alteration in a relative magnitude or delimited whole with 
unity of formal act. Relations are grounded in the mode in 
which a modifies b, b is modified by a, or the mode in which 
a and b modify each other. The intellect reflecting on itself 
may abstract these relations and consider them under the rubric 
of typical properties, such as reflexiveness, asymmetry, sym- 
metry, transitiveness, etc.; but relations reduce to their terms, 
namely, substances. Relations do not possess a being over and 
above their natural concretion in things. 


Where the proper accidents are unknown, and hence the 
essential form remains undetermined, the mode of assertion is 
by way of accidental accidents. In such cases the necessary 
mode of being is indeterminate in analysis due to the obscurity 
of natural processes. Under such circumstances the compos- 
sibility of essence to existence is not established, and the tran- 
scendental predicates cannot be conveniently measured in the 
adequation of the thing to the intellect. Such modes are rather 
like protocols of arbitrary aggregates or confused first inten- 
tions awaiting admission by some knack of theory and experi- 
ment to the certified status of an essence. The necessary acci- 
dents are those without which the subject cannot exist, whereas 
the contingent accidents may or may not be present without 
affecting the essential mode of substantial being. Contingent 
accidents therefore result in accidental units, the essential 
order of act to potency is unknown. In general, then, properties 
derived from the essence issue from the constitutive principle of 
the natural being, or the necessarily disposed order of act and 
potency, but the contingent aspects are derived from certain 
particular dispositions of the matter as a margin of potentiality 
beyond the essential form. Where the essence is known the 
contingent accidents may be considered as completions of in- 
dividuality extrinsically received, and where it is not known 
they are not univocal signs of many. 

And now a word about angels. Angels are beings not literally 
knowable to man as corporeal substances are knowable, and 
hence they must be understood by analogy. They are like 
material natures according as such natures have an essence, but 
they are unlike such natures in that corporeal natures are com- 
posited of matter and form. But it has been said that all cases 
of matter and form are instances of potency and act, and that 
this is not simply convertible. The angels have potency and act 
without having matter and form. They possess essence and 


existence, and the angelic essence is its existence, so that con- 
sequently there is not a material distinction of that which and 
that by virtue of which respecting their being. An angel is 
simultaneously all that it can be without any margin of mate- 
rial potentiality. Unlike man, an angel does not approach its 
essence discursively or by successive operations. 

The perfection of an angel follows immediately from its 
grade of being, which is its grade of knowing. An angel under- 
stands by a single intuition or immediate illumination. Its 
potency arises from the fact that its being is not a se, but de- 
rived from God as such a mode of perfection or measure of 
being in act in the order of creation. The Cartesian postulate 
for substance: res quae ita exsistit ut nulla alia re indigeat ad 
existendum* will not suffice to define substance clearly in the 
finite order since it omits the ordination of the finite to that 
which conditions it in its order. Accordingly, if an angel exists 
per se and in se it does so as a certain autonomy of completed 
act received from God, and it is a simultaneously actualized 
measure of act. But it is a finite measure, so that accordingly 
its potentiality may be understood since, though it is such a 
measure of act, the measure is apart from the pure act which 
is God. A partial measure is not equivalent to the whole. 

Since an angel is without any admixture of matter, standing 
as it does at a fixed distance or remotion from matter, its species 
cannot be multiplied into many according to the quantifying 
principle of matter. The specific act of the angel is one and the 
same with its existence and inseparable therefrom, so that it is 
a species one and distinct. There is then not a multiplication of 
individuals after the kind of a species, but it can be said that 
there is more than one angel, since a species is determined by 
the addition of a unit as indeed one number is differentiated 

6 "A thing which exists in such a way that it requires no other in order 
to exist." Descartes. Princioia Philosoohiae. i. . 


from another by the addition of a unit. Thus one angel differs 
from another by the addition of an operation. In addition, a 
being differs from another being according as in one being 
there is a reduction of multiple operations to a few unified 
operations, the being with greater operative unity excelling in 
measure of perfection the being with less. Any being possesses 
a constitutive principle by virtue of which it is that which it is 
and performs that which it performs its proper perfection. 
Each creature exists by its assigned act and proper perfection. 
The more an active and operative power is elevated in dignity, 
the more noble it is, the more power it includes and compounds 
in itself. Angels are such magnitudes of power completely ac- 
tualized. "Ordo rerum tails esse invenitur ut ab uno extreme 
ad alterum non perveniatur nisi per media" 7 

The Latin text of the De Ente et Essentia used for this 
translation is the critical edition of M.-D. Rolland-Gosselin, 
O. P., LE "DE ENTE ET ESSENTIA" de S. Thomas 
d'Aquin (Texte etabli d'aprs les manuscrits parisiens.), Bib- 
liotheque Thomiste VIII, Le Saulchoir, Kain, Belgique, 1926. 
This edition, which includes an introduction, notes and his- 
torical comments, is fully authenticated and corrected. 

Footnotes have been confined to the citation of the text locus 
when an author or quotation appears in the translation. Refer- 
ences: Aristotle, any standard text, but preferably in Greek or 
Latin; Avicenna, Opera... per canonicos (S. Augustini) emen- 
data, Venise 1508; Averroes, Aristotelis . . . Opera . . . Averrois 
Cordubensis in ea opera . . . comentarri, Venetiis, in 4, T. I., 
1552 et seq.; Boethius, M. S. Boetii Opera Omnia, T. 2. Migne 

7 Further concerning the Angelology, cf. Summa Theologica and the 
Summa Contra Gentes. (English trans, by the Dominican Fathers, Lon- 
don, Burns, Gates & Washbourne Ltd.; Benzigcr Bros., New York.) 

PREFACE xliii 

P. L., t. 182. M. Grabmann, fitienne Gilson and P. Mandonnet 
belong to the 'star chamber' of modern critics and commenta- 
tors. For the beginner, who may find the text slightly obdurate, 
I recommend: An Introduction to Philosophy, by Jacques Mari- 
tain, Sheed and Ward, 1933. Because of the parallel doctrine, 
not to speak of its excellent conception, I also mention: The 
Logic of William of Oc1(ham 9 Ernest Moody, Sheed and Ward, 

According to Dante in The Convivio Latin is a conventional 

language, especially designed for stability and catholicity in 
order to reduce the confusion of the Tower of Babel. The 
vulgar tongue follows fluid usage, but the Latin follows pre- 
meditated art. This places a special charge upon the translator. 
The De Ente is an argument in the strictest sense. Its object 
is to demonstrate propositions and to invoke concepts. One may 
expect the restrained severity of demonstration, the repetitive 
convention of basic propositions as in a geometrical proof, and 
finally the cumulative persuasion of expanded meaning result- 
ing from ordered syllogisms. In such expositions stylish word 
variations, pleonasms, and in short the whole apparatus by 
which modish writers puff the contours of their writings ob- 
scure the clarity and integrity of principles. Accordingly, the 
translator has confined paraphrase to the preface and has sought 
to adhere to the precise meaning of the text and thus to render 
a metaphrase even at the expense of awkward expression. 

In general the Latinity of St. Thomas, inherited from Cicero 
and Boethius, passes with a just retention of meaning into 
English. I have rendered all of the technical terms by English 
equivalents, thus avoiding a certain esoteric manner of trans- 
lators which makes for obscurantism, since not the words as 
such, but the concepts promoted by the context, "the discourse 
within the soul", are the proper vehicles of intelligence. In 
sundry places where the word ratio appears, it has been trans- 


lated ratio rather than by some accredited English term, as, 
for example: notion, concept, idea, rationale, principle, etc. The 
ratio of genus, species and difference is in effect a reference in 
intentions; nor would one speak of the notion, rationale, etc. 
of 2 : 4. An essence in one sense may be compared to a set of 
ratios and thus like an equation in mathematics has a typical 

The rough draft of this translation was first made for my 
own use in 1934-1935 during my academic year at Yale Uni- 
versity as the Sterling Fellow in philosophy^ consequently, I 
wish to acknowledge the opportunity which the fellowship 
afforded me. To Dr. Lewis M. Hammond, with whom the 
translation of the first part of the opusculum was begun, I owe 
a debt of initiation. For her assistance throughout with the 
burden of translation, and especially for her precise insights 
as to modes of rendition, a special measure of appreciation is 
due to my wife. Professor Scott Buchanan has contributed much 
to my appreciation of Greek and Scholastic methods, but I 
should be pained to suppose that any errors of mine might be 
attributed to anyone except myself. 


Amherst Court House, 




"BECAUSE a small error in the beginning is a great one in the 
-*-* end, according to the Philosopher in the first book of the 
De Caelo et Mundo? and since being and essence are what are 
first conceived by the intellect, as Avicenna says in the first 
book of his Metaphysics, 2 therefore, lest error befall from ig- 
norance of them (being and essence), in order to reveal their 
difficulty it should be said what is signified by the names being 
and essence, and how they are found in diverse things and 
how they are disposed with respect to (se habeant ad) logical 
intentions, namely, genus, species, and difference. 

1 Aristotle, De Caelo et Mundo, A, 271 b 8-13. 

2 Avicenna, Metaphysics, Tr. I, Cap. 6, f. 72 b A. 


BECAUSE indeed we must receive knowledge of the simple 
from the composite and arrive at what is prior from what 
is posterior, in order that beginning with the less difficult in- 
struction may be made more suitably, we should proceed from 
the meaning of being to the meaning of essence. 

Therefore one should know, as the Philosopher says in the 
fifth of the Metaphysics? that being by itself (ens per se) is 
said to be taken in two modes: in the one mode, that it is 
divided into ten genera; in the other, that it signifies the truth 
of propositions. Moreover the difference between these is that 
in the second mode everything can be called being concerning 
which an affirmative proposition can be formed, even if it 
posits nothing in the thing (in re}\ by virtue of this mode 
privations and negations are likewise called beings, for we say 
that affirmation is the opposite of negation, and that blindness 
is in the eye. But in the first mode only what posits something 
in the thing can be called being; consequently, according to 
the first mode blindness and such are not beings. The name 
essence, therefore, is not taken from being in the second mode, 
for in this mode some things are said to have essence which 
have not being, as is evident in privations, gut essence is taken 
from being only in the first mode; whence the Commentator 
says in the same place that 4 "being in the first mode is said 
to be what signifies the essence of the thing." And because, as 
has been said, being in this mode is divided into ten genera, 

8 Aristotle, Metaphysics, A> io j 7 a 22-35; a ^ s Met, E, b 17-35. 
4 Averroes, In Met. L.V., Comm. 14, f. 55 a 56. 



it follows that essence signifies something common to all na- 
tures by which diverse beings are disposed in different genera 
and species, as for instance humanity is the essence of man 
and so for others. And because that by means of which the 
thing is constituted in its proper genus or species is that which 
is signified by the definition indicating what the thing is, hence 
it is that the name essence has been changed by philosophers 
into the name quiddity. And this is what the Philosopher fre- 
quently calls "quod quid erat esse" 5 that is, that by virtue of 
which a thing (anything) has to be what it is (something), 
(id li fjv elvai). And indeed it is called form according as by 
means of form the certitude of any single thing is signified, 
as Avicenna remarks in the second part of his Metaphysics* 
This is called by another name, nature, accepting nature ac- 
cording to the first of the four modes assigned by Boethius in 
his book DC Duabus Naturis? namely, according as nature is 
said to be all that which can be comprehended by the intellect 
in any mode whatsoever; for a thing is not intelligible except 
by virtue of its definition and essence. And thus also the 
Philosopher in the Fourth book of his Metaphysics* says that 
every substance is a nature. But the name nature taken in this 
sense is seen to signify the essence of a thing inasmuch as it 
has a disposition (ordinem) towards an operation proper to 
the thing, since no thing is lacking in its proper operation. 
Indeed the name quiddity is taken from that which signifies 
the definition; but it is called essence according as by virtue 
of it and in it being has existence (esse). 

But because being is asserted absolutely and primarily of 

5 Aristotle, An. Post. I, 22, 82 b 38; De An. Ill, 6, 430 b 28; Met, Z, 
1028 b 34. 

6 Avicenna, perhaps Met. Ill, 5, f. 80 b; certitudo: essence. 

7 Boethius, De Persona et Duabus Nat, c. I, PL, t. 64, col. 134160. 

8 Aristotle, Metaphysics, A> 1014 b 35. 


substances and secondarily and as if in a certain respect 
(secundum quid) of accidents, hence it is that essence also 
exists truly and properly in substances, but exists in accidents 
in a certain mode and in a certain respect. Some substances 
indeed are simple and others are composite, and in both there 
is an essence. But essence is possessed by simple substances in 
a truer and more noble mode according as simple substances 
have a more exalted existence, for they are the cause of those 
which are composite, at least the primary substance, which is 
God, is. But since the essences of these substances are more 
concealed from us, therefore we must begin from the essences 
of composite substances in order that instruction may be made 
more suitably from what is easier. 


IN COMPOSITE substances, therefore, matter and form are 
noted, as for instance in man soul and body are noted. 
Moreover it cannot be said that either of these alone is called 
essence. For it is evident that matter alone is not the essence 
of the thing, because it is by means of its essence that the thing 
is both known and ordered in its species and genus. But matter 
is not the principle of cognition, nor is anything determined as 
regards genus and species according to it (matter), but accord- 
ing to that by means of which something is in act. And fur- 
thermore neither can form alone be called the essence of com- 
posite substance, however much some attempt to assert this. 
From what has been said it is clear that essence is what is 
signified by the definition of the thing. But the definition of 
natural substances contains not only form but also matter; for 
otherwise natural definitions and mathematical definitions 
would not differ. Nor can it be said that matter is posited in 
the definition of a natural substance as an addition to its essence 
or as a being outside of its essence (extra essentiam), since this 
mode of definition is mere proper to accidents which do not 
have a perfect essence; whence it follows that they must admit 
the subject into their definition, which (subject) is outside of 
their genus. It is clear, therefore, that essence comprehends 
matter and form. But it cannot be said that essence signifies a 
relation which is between matter and form, or that it is some- 
thing superadded to them, since something superadded would 
of necessity be accidental or extraneous to the thing, nor could 
the thing be conceived by means of it, for everything is appro- 



priate to its essence. For by the form, which is the actuality of 
matter, matter is made being in act and a this somewhat. 
Whence that which is superadded does not give existence (essc) 
in act simply to matter, but existence in act of such sort as 
likewise accidents make, as for instance whiteness makes some- 
thing white in act. Wherefore whenever such form is acquired 
it is not said to be generated simply but in a certain respect 
(secundum quid). Hence it follows that in composite sub- 
stances the name of essence signifies that which is composed 
of matter and form. And this agrees also with the opinion of 
Boethius in his commentary Predicamentorum? where he says 
that ousia signifies a composite. For ousia according to the 
Greeks is the same as essence according to us, as Boethius him- 
self remarks in his book De Duabus Naturis. 10 Avicenna also 
says 11 that the quiddity of composite substances is itself a 
composition of matter and form. The Commentator also says 
concerning the seventh book of the Metaphysics 12 : "The na- 
ture which species have in things capable of generation is 
something intermediate that is composed of matter and form." 
Reason also accords with this, because the existence of a com- 
posite substance is not the existence of form only, nor the 
existence of matter only, but of the composite itself; and indeed 
essence is that according to which a thing is said to exist. 
Whence it follows that the essence by virtue of which a thing 
is called being is not form alone, nor matter alone, but both; 
although in its mode the form is the cause of its existence. We 
discover it indeed thus in other things which are constituted 
from more than one principle, since a thing is not named from 
one of those principles alone, but from that which unites both. 

9 In Cat. I, De Substantia, PL, t. 64, col. 184 A. 

10 DC Persona et Duabus, Nat, PL, t. 64, col. 1344 C. D. 

11 Avicenna, Met, V, 5, f. 90 a F. 

12 Averrocs, In Met, VII, c. 7, comm. 27, f. 83 a 41. 


It appears thus in the case of tastes, because sweetness is caused 
from the action of warmth dissolving moisture, and although 
in this mode the warmth is the cause of the sweetness, yet a 
body is not called sweet from its warmth but from the taste 
which unites both the warmth and the moisture. 

But because the principle of individuation is matter, it per- 
haps seems to follow from this that essence which unites in 
itself both matter and form would be only particular and not 
universal. From this it would follow that universals do not 
have definition, if essence is what is signified by means of the 
definition. One should therefore understand that matter in any 
mode whatsoever is not taken to be the principle of individua- 
tion, but only signaled matter (materia signata). And I call 
signaled matter that which is considered as under determinate 
dimensions. But now this matter is not posited in the defini- 
tion of man inasmuch as he is man, but it would be posited 
in the definition of Socrates if Socrates were to have a defini- 
tion. But in the definition of man non-signated matter is 
posited; for in the definition of man this certain flesh and this 
certain bone are not posited, bu\ bone and flesh absolutely, 
which are the non-signated matter of man. Accordingly, it is 
clear that the essence of Socrates and the essence of man do not 
differ except according to signate and non-signate. Whence the 
Commentator remarks upon the seventh of the Metaphysics 13 : 
"Socrates is nothing other than animality and rationality which 
are his quiddity/' Thus also the essence of genus and of species 
differ according to signate and non-signate, although there is a 
different mode of designation for each of them, because the 
designation of the individual with respect to species is by 
means of matter determined by dimensions, whereas the desig- 
nation of species in respect to genus is by means of the consti- 
tutive difference which is take/i from the form of the thing. 

18 Avcrroes, In Met, VII, 5, comm. 20, f. 80 a 23. 


This determination or designation, however, which is in the 
species in respect to genus is not by means of something exist- 
ing in the essence of species, which is in no mode in the essence 
of genus; nay, whatever is in species is in genus as something 
undetermined. For if animal is not the whole of man, but part 
of him, it is not predicated of him, since no integral part is 
predicated of its whole. 

But how this is related can be seen if one observes how body 
differs according as animal is posited as part or as genus; for 
it cannot be genus in the same mode in which it is an integral 
part. This name body, therefore, is taken in several senses. For 
body according as it is in the genus of substance is asserted of 
that which has a nature such that three dimensions can be 
designated in it; in truth the three designated dimensions them- 
selves are body which is in the genus of quantity. But it hap- 
pens in things that what has one perfection may also aim at 
further perfection; as for instance is clear in the case of man, 
since he has both a sensitive nature and further, intellectual 
nature. Likewise indeed beyond this perfection which is to have 
such a form that three dimensions can be designated in it, 
another perfection can be added, as life or something of this 
sort. This name body, therefore, can signify a certain thing 
which has a form such that from it follows the possibility of 
designating three dimensions in it, with this limitation, 
namely, that from that form no further perfection may follow, 
but if anything else is added it is beyond the significance of 
body thus spoken of. And in this mode body is an integral and 
material part of animal, because thus soul will be beyond what 
is signified by the name body and will be something added 
to (excelling) body itself in such wise that from these two, that 
is, from soul and body, the animal is constituted as from its 
parts. This name body can also be taken so as to signify a 
certain thing which has a form such that from the form three 


dimensions can be designated in it, whatsoever that form may 
be, and whether any further perfection can issue from it or not. 
And in this mode body is the genus of animal, because in 
animal nothing is taken which is not contained implicitly in 
body; for soul is not a form different from that by means of 
which three dimensions can be designated in that thing. And 
therefore when it was said that body is what has a form such 
that from the form three dimensions can be designated in the 
body, it was to be understood of whatever the form might be, 
whether animality or lapidity or any other. And so the form of 
animal is contained implicitly in the form of body, according 
as body is its genus. And such too is the habitude (relation) of 
animal to man. For if animal denoted only a certain thing 
which has a perfection such that it can feel and be moved by 
virtue of a principle existing in itself, to the exclusion of any 
further perfections, then whatever further perfection super- 
vened to the thing, would be disposed in respect to (haberet 
se ad) animal by means of the partitive mode (modum partis) 
and not as if implicitly beneaxh (included in) the principle of 
animal, and thus animal would not be a genus. But animal is 
a genus according as it signifies a certain thing from the form 
of which can issue feeling and motion, whatsoever this form 
may be, whether it be the sensible soul alone or the sensible 
and rational together. Thus, therefore, genus signifies indeter- 
minately all that which is in species, for it does not signify mat- 
ter alone. Similarly, difference signifies the whole, but it does 
not signify form alone. And definition likewise signifies a 
whole, and also species does. But yet in diverse ways: because 
genus signifies a whole as a certain determination determining 
what is material in a thing, without the determination of the 
proper form. Whence genus is taken from matter, although it is 
not matter, as is evident in the instance of what is called body 
because it has a perfection such that three dimensions can be 


designated in it, which certain perfection is materially disposed 
towards further perfection. In truth, on the contrary, difference 
is taken determinately as a certain determination by form, for 
the reason that determined matter is involved in the primary 
conception of it, as appears when it is called animate or that 
which has soul; for what it is, whether body or something else, 
is not determined. Whence Avicenna says 14 that genus is not 
intellected in difference as a part of essence, but only as a being 
beyond its essence (extra essentiam), just as a subject is in re- 
gard to the intellection of the passions. And therefore, likewise, 
speaking per se, genus is not predicated concerning difference, 
as the Philosopher remarks in the third of the Metaphysics 16 
and the fourth of the Topics, unless perchance as a subject is 
predicated of passion. But definition or species comprehends 
both, namely, determinate matter which the name of genus 
designates, and determinate form which the name of difference 

And from this the reason is clear why genus and species and 
difference are proportionally disposed towards (se habeant ad) 
matter and form and the composite in nature, although they 
are not the same as nature, since genus is not matter but taken 
from matter as signifying the whole, nor is difference form but 
taken from form as signifying the whole. Wherefore we call 
man a rational animal, not from the composite of animal and 
rational, as we say that he is composed of body and soul; for 
man is said to be composed of soul and body, just as from two 
things a third thing is truly constituted, which is neither of 
the two; for man is neither soul nor body. But if man can be 
said to be composed in some manner of animal and rational, 
it is not as a third thing from two things but as a third concept 
from two concepts; for the concept of animal is one expressing, 

i* Met, V, 6, f, 90 a BC. 
16 Aristotle, Met, B, 998 b 24. 


without the determination of a special form, the nature of a 
thing, by that which is material in respect to its ultimate per- 
fection. The concept, however, of the difference rational con- 
sists in the determination of a special form. And from the two 
concepts (animal and rational) is constituted the concept of the 
species or definition. And therefore just as a thing constituted 
from other things does not take the predication of those things, 
thus neither does the concept take the predication of those con- 
cepts from which it is constituted, for we do not say that the 
definition is genus or difference. 

But, although genus signifies the whole essence of species, 
yet it does not follow that there is one essence of different 
species which have the same genus, because the unity of the 
genus proceeds from its very indetermination and indifference; 
not, however, because that which is signified by genus is one 
nature by number in different species to which supervenes 
something else which is the difference determining it, as for 
instance form determines matter which is numerically one; 
but because genus signifies some form, though not determi- 
nately this or that (form) which difference expresses deter- 
minately, which is none other than that (form) which is 
signified indeterminately through genus. And therefore the 
Commentator says in the twelfth book of the Metaphysics 
that prime matter is called one through the remotion of all 
forms (scil. pure potentiality in the order of substance), but 
genus is called one through the community of its signified 
form. Whence it is clear that by means of the addition of 
difference, which removes the indetermination which was the 
cause of the unity of genus, species remain different by virtue 
of essence. 

And because, as has been said, the nature of species is in- 
determinate in respect to the individual, just as the nature of 

16 Averroes, In Met, XII, c. 14, f. 141 a 53 b 18. 


genus is indeterminate with respect to species, hence it is that, 
just as that which is genus according as it is predicated con- 
cerning species implies in its signification, although indis- 
tinctly, all that is determinate in species, thus likewise it fol- 
lows that what is species, according as it is predicated of the 
individual, signifies all that which is in the individual essen- 
tially although indistinctly. And in this mode the essence of 
Socrates is signified by the name of man, and as a consequence 
man is predicated of Socrates. But if the nature of the species 
be signified with the exclusion of designated matter, which is 
the principle of individuation, it will thus be disposed (se 
habebii) as a part (by means of the partitive mode). And in 
this mode it is signified by the name humanity, for humanity 
signifies that in virtue of which man is man. But designated 
matter is not that in virtue of which man is man; and, there- 
fore, in no mode is it contained among those things from 
which man possesses manness. Since therefore humanity in- 
cludes in its concept only those things from which man pos- 
sesses manness, it is clear that designated matter is excluded 
from or cut off from its signification. And since the part is not 
predicated of the whole, hence it is that humanity is not predi- 
cated either of man or of Socrates. Wherefore Avicenna says 1T 
that the quiddity of a composite is not the composite itself of 
which it is the quiddity, although the quiddity itself is com- 
posite; as for instance humanity, although it is composite, still 
is not man. Nay rather, it must be received in something which 
is designated matter. But since, as has been said, the designa- 
tion of species in respect to genus is by virtue of form, whereas 
the designation of the individual in respect to species is by 
virtue of matter, it follows therefore that the name signifying 
that whence the nature of genus is taken, with the exclusion of 
the determinate form perfecting the species, should signify the 
17 Avicenna, Met., V, c. 5, f. 90 a F. 


material part of the whole itself, as the body is the material 
part of man. But the name signifying that whence the nature 
of species is taken, with the exclusion of designated matter, 
signifies the formal part. And therefore humanity is signified 
as a certain form, and is spoken of as that which is the form 
of the whole; not indeed as if it were superadded to the essen- 
tial parts, namely, to form and matter, as for instance the form 
of a house is superadded to its integral parts; but rather it is 
form that is the whole, that is, embracing form and matter, 
yet with the exclusion of those things by means of which mat- 
ter is found to be designated. So, therefore, it is clear that the 
name man and the name humanity signify the essence of man, 
but in different modes, as has been said, since the name man 
signifies it as a whole, inasmuch as it does not exclude the 
designation of matter but contains it implicitly and indis- 
tinctly, as for instance it has been said that the genus contains 
the difference. And therefore the name man is predicated of 
individuals. But the name humanity signifies the essence as a 
part, since it does not contain in its signification anything ex- 
cept what is of man inasmuch as he is man, and because it ex- 
cludes all designation of matter; whence it is not predicated 
of individual man. And for this reason likewise the name 
essence sometimes is found predicated of a thing, for Socrates 
is said to be an essence, and sometimes it is denied, as for in- 
stance it is said that the essence of Socrates is not Socrates. 


HAVING seen, therefore, what is signified by the name of 
essence in composite substances, we should see in what 
mode it is disposed towards (se habeat ad) the ratio of genus, 
species, and difference. Since, however, that to which the ratio 
of genus or species or difference applies is predicated concern- 
ing this signate singular, it is impossible that the ratio of the 
universal, namely, that of genus and of species, should apply 
to essence according as it is signified by means of the partitive 
mode, as for instance by the name humanity or animality. And 
therefore Avicenna says 18 that rationality is not the difference, 
but the principle of difference. And for the same reason hu- 
manity is not species nor is animality genus. Similarly, also, it 
cannot be said that the ratio of genus or of species applies to 
essence according as essence is a certain thing existing apart 
from singulars, as the Platonists were accustomed to assert, 
since thus genus and species would not be predicated of this 
individual. For it cannot be said that Socrates is what is sepa- 
rated from him, nor again that the separated conduces to the 
cognition of a singular. And therefore it follows that the ratio 
of genus or species applies to essence according as it is signified 
in the mode of a whole, as for instance by the name of man 
or animal, according as it contains implicitly and indistinctly 
all that is in the individual. 

But nature or essence taken thus can be considered in two 
ways. In one mode according to its proper ratio, and this is 
the absolute consideration of it, and in this mode nothing is true 

18 Avicenna, Met., V, 6, f. 90 b A. 



concerning it except what applies to it according to this mode, 
whence whatever else is attributed to it is a false attribution. 
For example, to man inasmuch as he is man rational and ani- 
mal applies and the other things which fall within his defini- 
tion. White or black, however, and whatsoever of this mode, 
which is not of the ratio of humanity, does not apply to man 
inasmuch as he is man. Accordingly, if it were asked whether 
this nature thus considered can be said to be one or more than 
one, neither ought to be conceded, because each is outside the 
concept of humanity, and either one can happen to it (ac- 
cidere). For if plurality were to belong to the concept of 
humanity, it could never be one although nevertheless it is one 
according as it is in Socrates. Similarly, if unity were to belong 
to its ratio, then would it be one and the same of Socrates and 
of Plato, nor could it be multiplied (plurificart) in many. It is 
considered in another mode according to the existence (essc) 
which it has in this or that, and in this mode something is 
predicated concerning it by means of accident (per accidens), 
by reason of that in which it is, as for instance it is said that 
man is white because Socrates is white, although this does not 
apply to man inasmuch as he is man. 

But this nature has a twofold existence: having one existence 
in singulars and another in the soul, and according to both of 
the two, accident follows upon the nature spoken of, and in 
singulars also it has a manifold existence according to the 
diversity of the singulars. And nevertheless to this very nature 
according to its primary consideration, that is to say, its abso- 
lute one, none of these (existences) ought to belong. For it is 
false to say that the essence of man, inasmuch as he is man, 
has existence in this singular, because if existence in this singu- 
lar applied to man as man, then (man) would never exist out- 
side of this singular. Similarly, also, if it applied to man as 
man not to exist in this singular, (man) would never exist in 


it. But it is true to say that man as man does not have to be 
in this singular or in that or in the soul. Therefore it is clear 
that the nature of man absolutely considered abstracts from any 
sort of existence, yet in such wise that it does not exclude any 
of them. And this nature so considered is what is predicated 
of all individuals. Still it cannot be said that the ratio of uni- 
versal applies to nature thus considered, because unity and com- 
munity belong to the principle of the universal, whereas to 
human nature neither of these (two) applies according to its 
absolute consideration. For if community belonged to the con- 
cept of man, then in whatsoever humanity were found com- 
munity would be found. And this is false because in Socrates 
there is not found any community, but whatever is in him is 
individuated. Similarly, also, it cannot be said that the ratio 
of genus or of species belongs to human nature according to 
the existence which it has in individuals, because human na- 
ture is not found in individuals according to its unity so that 
it is a one appropriate to all, which the ratio of the universal 
demands. It follows, therefore, that the ratio of species applies 
to human nature according to that existence (esse) which it 
has in the intellect. For human nature itself has an existence 
in the intellect abstracted from all individuations, and there- 
fore it has a uniform ratio to all individuals which are outside 
the soul, according as it is equally the likeness (similitude)} 
of all and leads to the understanding of all inasmuch as they 
are men. And because it has such a relation to all individuals, 
the intellect discovers the ratio of species and attributes it to it 
(human nature). Whence the Commentator observes in the 
first book of the De Anima 10 that intellect is what actuates 
(agit) universality in things. Avicenna also says this in his 
Metaphysics. Whence, althougn this intellectual nature has 

19 Averroes, In DC An., I, com. 8, f. 4. 

20 Avicenna, Met., V, i, f., 87 b E, 87 a C- b D. 


the ratio of universal according as it is compared to things 
which are outside of the soul because it is a single likeness of 
all, nevertheless according as it has existence in this intellect 
or that it is a certain particular intellected species. And there- 
fore the error of the Commentator in book three on the De 
Anima 21 is clear, seeing that he wished to conclude from the 
universality of the intellected form to the unity of the intel- 
lect in all men; because there is no universality of that form 
according to the existence which it has in the intellect, but 
according as it is referred to things as a likeness of things. 
Thus, too, if there were a single corporeal statue representing 
many men, it is clear that the image or species of the statue 
would have an existence singular and proper according as it 
existed in this matter, but it would have a ratio of cqmmunity 
according as it were a common thing representing many. And 
because to human nature according to its absolute consideration 
belongs what is predicated of Socrates, and since the ratio of 
species does not belong to it according to its absolute consider- 
ation, but follows from accidents which issue from it accord- 
ing to the existence which it has in the intellect, therefore the 

tjrif jf/ 

name of species is not predicated of Socrates so that it is said 
that Socrates is a species, which would necessarily happen if 
the ratio of species belonged to man according to the existence 
which he has in Socrates, or according to man's absolute con- 
sideration, namely, inasmuch as he is man; for whatever applies 
to man inasmuch as he is man is predicated of Socrates. Yet 
to be predicated applies to genus by virtue of itself (per se\ 
since it is posited in its definition. For predication is a certain 
thing which is perfected by means of the action of the intellect 
composing and dividing, having in the very thing as its founda- 
tion the unity of those things of which one is asserted of the 
other. Whence the ratio of predicability can be included in the 
21 Avcrrocs, In DC An., Ill, com, 5, f, 117. 


ratio of this mode of intention which is genus, which, simi- 
larly, is perfected by means of an act of the intellect. Yet, never- 
theless, that to which the intellect attributes the intention of 
predication, composing the one with the other, is not the very 
intention of genus but rather that to which the intellect at- 
tributes the intention of genus, as for instance what is signified 
by the name animal. Thus, therefore, it is clear how essence or 
nature is disposed towards (se habet ad) the ratio of species, 
because the ratio of species does not belong to those things 
which are appropriate to it according to its absolute considera- 
tion, nor likewise does it belong to the accidents which issue 
from it according to the existence which it has outside the soul, 
as whiteness or blackness. But it does belong to the accidents 
which issue from it according to the existence which it has in 
the intellect. And it is according to this mode that the ratio of 
genus and of difference also applies to it. 


Now IT remains to see through what mode essence exists in 
separate substances, namely, in the soul, in intelligences 
and in the first cause. But although all grant the simplicity of 
the first cause, yet certain ones strive to introduce a composi- 
tion of form and matter in intelligences and in the soul. The 
author of this position appears to have been Avicebron, the 
writer of the book Fons Vitae? 2 But this is opposed to what 
is commonly said by philosophers, seeing that they call them 
substances separated from matter and prove them to be devoid 
of all matter. The most powerful reason for the assertion is 
(taken) from the power (yirtute) of understanding which is 
in them (separate substances). For we see that forms are not 
intelligible in act except according as they are separated from 
matter and its conditions, nor are they made intelligible in act 
except by the power (per vlrtutem) of intelligent substance, 
inasmuch as they are received in it and inasmuch as they are 
actuated by virtue of it. Whence it is necessary that in any 
intelligent substance there be entire immunity from matter in 
such wise that they neither have a material part to them nor 
yet exist as a form impressed in matter, as is the case respecting 
material forms. Nor can anyone say that intelligibility is not 
impeded by any sort of matter, but only by corporeal matter. 
For if this impediment were by reason of corporeal matter 
alone, since matter is not spoken of as corporeal except inas- 
much as it stands under corporeal form, then it would follow 

22 Cf. Bacumkcr, Avcnccbrolis (Ibn Gcbirol), Fons Vitae, Munstcr, 



necessarily that matter would impede intelligibility by means 
of its corporeal form. And this cannot be, because the very 
corporeal form also is intelligible in act, just as other forms 
are, inasmuch as it is abstracted from matter. Wherefore in the 
soul or in an intelligence there is in no way a composition of 
matter and form so that essence might be taken in them in the 
mode in which it is taken in corporeal substances. But there 
is there (in them) a composition of form and existence; whence 
it is said in the comment on the ninth proposition of the book 
De Causis 23 that intelligence is having form and existence; 
and form is taken there for the very quiddity or simple nature. 
But it is easy to see how this is. For whatever things are 
disposed towards (se habent ad} one another in such wise that 
one is the cause of the existence of the other, that which has 
the ratio of cause can possess existence without the other, but 
not conversely. But such is found to be the habitude of matter 
and form, because form gives existence to matter, and therefore 
it is impossible for matter to be without some form, yet it is 
not impossible for any form to exist without matter, for form 
inasmuch as it is form does not depend on matter. But if any 
forms should be discovered which cannot exist save in matter, 
this happens to them inasmuch as they are distant from the 
first principle which is the first and pure act. Whence those 
forms which have the greatest propinquity to the first principle 
are forms subsisting by virtue of themselves (per se) without 
matter. For form does not require matter according to its entire 
genus, as has been said, and forms of this sort are intelligences. 
And therefore it is not necessary that the essences or quiddities 
of these substances be anything save the very form. Therefore 
the essence of a composite substance and the essence of a simple 

* 8 Cf. Bardenhewer, "Die pscudoaristotelische Schrift tJbcr das Reinc 
Cute" bckannt untcr dcm Namen "Liber de Causis", Fibourg-en-Bas, 
i&8a, No. 8, p. 173. 


substance differ in that the essence of a composite substance 
is not form alone but embraces form and matter, whereas the 
essence of a simple substance is form alone. And from this two 
other differences are derived. One is that the essence of a com- 
posite substance can be signified as a whole or as a part, which 
happens according to the designation of the matter, as has been 
stated. And therefore the essence of a composite thing is not 
predicated in any mode whatsoever of the composite thing 
itself; for it cannot be said that man is his quiddity. But the 
essence of a simple thing, which is its form, cannot be signified 
except as a whole, since there is nothing there except the form 
as form receiving, and, therefore, in whatever mode the essence 
of a simple substance is taken it is predicated of the substance. 
Whence Avicenna says 24 that the quiddity of a simple (sub- 
stance) is itself simple, because there is not anything else 
receptive of the quiddity. The second difference is that the es- 
sences of composite things, seeing that they are received in 
designated matter, are multiplied according to its division, 
whence it results that some things are the same in species and 
diverse numerically. But since the essence of simple substance 
is not received in matter, there cannot be there any such mul- 
tiplication. And therefore it follows necessarily that in these 
substances more than one individual of the same species are 
not found, but however many individuals there are, just so 
many are the species, as Avicenna expressly says. 25 (scil. "A 
species of this mode is one in number.") 

And indeed substances of this sort, although they are forms 
alone without matter, still do not have an entire simplicity 
of nature so that they are pure act; on the contrary, they have 
a mixture of potency, which is evident thus: for whatsoever 
does not belong to the concept of essence or quiddity is some- 

24 Avicenna, Met., V, 5, f. 90 a F. 

25 Avicenna, Met., V, 2, f. 87 a A. 


thing accruing from without and effecting a composition with 
the essence, since no essence can be conceived without those 
things which are parts of essence. But every essence or quiddity 
can be conceived aside from the condition that something be 
known concerning its existence, for I can conceive what a man 
or phoenix is and still not know whether it has existence in the 
nature of things. Therefore it is clear that existence is some- 
thing other than essence or quiddity, unless perhaps there be 
something the quiddity of which is its very existence. And 
this thing can only be one and primary, because it is impossible 
that a multiplication of anything should be effected except by 
virtue of the addition of some difference, as the nature of genus 
is multiplied into species either by virtue of this, that the form 
is received in diverse matters, just as the nature of species is 
multiplied in diverse individuals, or by virtue of this, that it is 
one thing absolutely but another as received in something, as 
for instance if there were a certain separated heat it would be 
other than a non-separated heat from its very separation. But 
if some thing is posited which is existence alone such that the 
existence itself is subsisting, this existence does not receive an 
addition of difference, since then it would not be existence only 
but existence and beyond that some form; and much less does 
it receive an addition of matter because then it would be not 
a subsisting existence but a material existence. Wherefore it is 
clear that a thing such that it is its own existence cannot be 
except as one (unique). Whence it follows necessarily that in 
anything whatsoever except this (the unique) its existence 
must be one thing and its quiddity or nature or form another. 
Accordingly, in intelligences there is an existence over and 
beyond form, and therefore it has been said that an intelli- 
gence is form and existence. 

But all that belongs to anything is either caused from prin- 
ciples of its nature, as for instance risibility in man, or accrues 


to it through some extrinsic principle, as for instance light in 
air from the influence of the sun. But it cannot be that existence 
itself should be caused by the form or quiddity of the thing, 
caused, I say, as by means of an efficient cause, because thus 
something would be the cause of itself and would bring its 
very self into existence, which is impossible. Therefore it fol- 
lows that everything such that its existence is other than its 
nature has existence from another (ab alia). And because every- 
thing which exists by virtue of another is reduced to that 
which exists in virtue of itself (per se) y as to its first cause, 
it follows that there must be something which is the cause of 
the existence {causa essendi) of all things, because it is very 
existence alone; otherwise the causes would proceed to infinity, 
since everything which is not existence alone would have a cause 
of its existence, as has been said. It is clear, therefore, that an intel- 
ligence is form and existence, and that it has its existence from the 
first being which is existence alone, and this is the first cause 
which is God. But everything which receives something from 
something (all quid ab all quo) is in potency in respect to that, and 
what is received in it is its act. Therefore it follows that the very 
quiddity or form which is the intelligence is in potency in 
respect to the existence which it receives from God, and that 
existence is received according to the mode of act. And thus 
potency and act are found in intelligences, yet not form and 
matter, except equivocally. Whence, too, to suffer, to receive, 
to be a subject and all things of this kind which are seen to 
belong to things by reason of matter, belong equivocally to in- 
tellectual substances and to corporeal substances, as the Com- 
mentator says in the third book of the De Animal And be- 
cause, as has been said, the quiddity of an intelligence is the 
intelligence itself, therefore its quiddity or essence is the same 
thing as itself, and its existence, received from God, is that by 
26 Avcrroes, In DC An., Ill, com. 14, f, 123. 


means of which it subsists in the nature of things. And for 
this reason substances of this sort are said by some to be com- 
posed of that by virtue of which it is (quo esi) and that which 
it is (quod est), or of that which it is and existence, as 
Boethius says. 27 

And since potency and act are posited in intelligences it will 
not be difficult to find a multitude of intelligences, which 
would be impossible if there were no potency in them. Whence 
the Commentator says in the third book of the De Anlrna^ 
that if the nature of the possible intellect were unknown we 
should not be able to discover multiplicity in separate sub- 
stances. Therefore the distinction of these in regard to one 
another is according to their grade (measure) of potency and 
act, so that a superior intelligence which is more proximate to 
the first (being) has more of act and less of potency, and so 
for others. And this is fulfilled in the human soul which holds 
the lowest grade among intellectual substances. Whence its 
possible intellect is disposed towards (se habet ad) intelligible 
forms just as first matter, which holds the lowest grade in 
sensible existence, is disposed towards sensible forms, as the 
Commentator remarks in book three on the De Animal And 
therefore the Philosopher 80 compares it to a tablet upon which 
nothing is written, and for this reason among other intelligible 
substances it has more potency. Accordingly, it is made to be 
so close to material things that the material thing is drawn to 
participate in its existence, so that from soul and body results 
one existence in one composite, although that existence accord- 
ing as it pertains to soul is not dependent upon the body. And 
therefore after that form which is in the soul are discovered 

27 Boethius, DC Hcbd., PL, t. 64, col. 1311 C. 

28 Avcrroes, In De An., Ill, com. 5, f. 118. 
29 Averroes, In DC An., Ill, com. 5, p. 113 
30 Aristotle, De An., Ill, 430 a i. 


other forms having more potency and more propinquity to 
matter. In these, too, is found order (ordo) and grade (meas- 
ure: gradus) all the way through to the first forms of elements 
which are in the greatest propinquity to matter. Accordingly, 
they do not have any operation except according to the 
exigency of active and passive qualities, and of the others by 
which matter is disposed to form. 


HAVING understood the above, one knows clearly how essence 
is found in different things. For there is a threefold way 
of having an essence in substances. One way is like God, whose 
essence is His very existence; and therefore some philosophers 
are found who say that God does not have a quiddity or 
essence, since His essence is none other than His existence. And 
from this it follows that God is not in a genus, since everything 
which is in a genus must have a quiddity in addition to its 
existence, seeing that the quiddity or nature of genus or species 
is not distinguished according to a principle of nature in those 
things of which it is genus and species, but existence is dif- 
ferent in different things. And indeed if we say that God is 
existence alone it is not necessary that we fall into the error 
of those who said that God is that universal existence in which 
everything exists formally. For the existence which is God is 
of a condition such that no addition can be made to it. Whence 
by virtue of its very purity it is existence distinct from every 
other existence, as for instance a certain separated color would 
by its very separation be different from non-separated color. 
For this reason it is observed in the comment on the ninth 
proposition of the book De Causis 81 that the individuation of 
the first cause which is existence alone is by means of its pure 
goodness. But common existence, just as it does not include 
an addition to its concept, so, too, does not include in its con- 
cept any exclusion of addition, because if this were so nothing 

31 DC Causis, cf. Bardcnhcwcr, op. cit., No. 8, p. i?3- 



could be conceived to exist in which something over and above 
were added to existence. Similarly, too, although a being be 
existence alone, it does not follow that it should be wanting in 
the rest of the perfections and nobilities. Indeed God has the 
perfections which are in all genera, and for this reason He is 
called perfect simply, as the Philosopher and Commentator say 
in the fifth book of the Metaphysics* 2 but He has these (per- 
fections) in a more excellent mode than other things, because 
in Him they are one, but in other things they have diversity. 
And this is because all of these perfections belong to Him 
according to his simple existence; just as, if someone were able 
by means of one quality to effect the operations of all qualities, 
in that one quality he would have all qualities, so God in His 
very existence has all perfections. 

According to the second mode essence is found in created 
intellectual substances in which the essence is other than their 
existence, although their essence is without matter. Whence 
their existence is not absolute but received and therefore accord- 
ing to the capacity of the receiving nature, but their nature or 
quiddity is absolute and not received in any matter. And there- 
fore it is said in the book De Causis 83 that intelligences are 
infinite from beneath and finite from above. For they are finite 
in respect to their existence which they receive from above, but 
they are not finite from below, since their forms are not limited 
to the capacity of any matter receiving them. And therefore in 
such substances there is not found a multitude of individuals in 
one species, as has been said, except in the instance of the 
human soul because of the body which is united to it. And 
although its individuation depends on the body as its occasion 
inasmuch as its (that of the individuation) beginning is con- 

82 Aristotle, Met, A, 1021 b 30; Averroes, In Met, V, com. 21, f. 62 
a 10-13. 

88 De Causis, cf. Bardenhewer, op. cit, No. 4, p. 167. 


cerned, seeing that the soul does not acquire individuated 
existence except in a body of which it is the act, still it does 
not follow that, the body being removed, the individuation 
would perish; because, since it (the soul) has absolute existence 
from the time individuated existence is acquired, in that it is 
made the form of this body, that existence always remains in- 
dividuated. And therefore Avicenna says 34 that the individua- 
tion of souls and their multitude depends upon the body in 
respect to their beginning but not in respect to their end. And 
because in those substances quiddity is not the same as existence 
therefore they are capable of being ordered in a predicament 
(category) and for this reason genus, species, and difference 
are found in them, although their proper differences are hid- 
den from us. For in sensible things likewise the essential dif- 
ferences themselves are unknown; hence they are signified by 
means of the accidental differences which arise from their 
essential differences, as a cause is signified by means of its 
effect, as for instance biped is posited as the difference of man. 
But the proper accidents of immaterial substances are not 
known to us, and accordingly their differences cannot be signi- 
fied by us either by virtue of themselves or by virtue of their 
accidental differences. 

Still one ought to know that genus and difference are not 
taken in the same mode in those substances and in sensible sub- 
stances, because in sensible substances genus is taken from that 
which is material in the thing, but difference is taken from 
that which is formal in it. Whence Avicenna says in the be- 
ginning of his book De Anima 85 that form in things composed 
of matter and form "is the simple difference of that which is 
constituted from it," not, however, so that the form itself is 
the difference, but because it is the principle of the difference, 

84 Avicenna, DC An., V, c. 3, f. 14 b. 
80 Avicenna, De An., I, i, f i b E xa. 


as he says in his Metaphysics?* And such difference is called 
simple difference, because it is taken from what is a part of 
the quiddity of the thing, namely, from the form. But since 
immaterial substances are simple quiddities, difference in them 
cannot be taken from that which is a part of the quiddity but 
from the whole quiddity. And therefore in the beginning of 
the De Anima 37 Avicenna says that "simple difference . . . 
is not possessed except in those species the essences of which 
are composed of matter and form." Similarly also in these sub- 
stances genus is taken from the whole essence, yet in a dif- 
ferent mode. For one separate substance agrees with others in 
immateriality, and these substances differ from one another in 
their grade of perfection according to their recession from 
potentiality and their accession to pure act. And therefore in 
them genus is appropriated from that which ensues from them 
inasmuch as they are immaterial, as intellectuality or something 
of this sort. Difference, however, is appropriated from that 
which ensues from the grade of perfection in them and this is 
unknown to us. And yet it is not necessary that these differ- 
ences be accidental, because they are according to greater and 
less perfection which does not diversify species; for the grade 
of perfection in receiving the same form does not diversify 
species, just as more white and less white in participating in 
the same principle of whiteness (does not), but a different grade 
of perfection in the very forms or natures participated does 
diversify species, as for instance nature proceeds by grades from 
plants to animals through certain (levels) which are mediate 
between animals and plants, according to the Philosopher in 
the eighth book of the De Animalibus?* Nor again is it neces- 
sary that the division of intellectual substances be always 

88 Avicenna, Met., V, 5, f. 90 b A. 

87 Avicenna, DC An., I, i, f. i b E. 

88 Aristotle, De Hist. Animal., VIII, 588 b 4-14. 


through two true differences, because it is impossible for this 
to happen in all things, as the Philosopher says in the eleventh 
book of the De Animalibus.** 

In the third mode essence is found in substances composed 
of matter and form, in which also existence is received and 
finite because they have existence from another, and again their 
nature or quiddity is received in signaled matter. And there- 
fore they are finite from above and below, and in them fur- 
thermore a multiplication of individuals in one species is pos- 
sible, because of the division of signaled matter. And how their 
essence is disposed towards (se habeat ad} logical intentions 
has been discussed above. 

89 Aristotle, DC Part. An., I, 642 b 5. 


IT NOW remains to see how essence exists in accidents, for 
how it exists in all substances has been discussed. And be- 
cause, as has been said, essence is what is signified by means of 
definition it is necessary that they (accidents) possess essence 
in the mode in which they have definition. But they have an 
incomplete definition because they cannot be defined unless a 
subject is posited in their definition; and this is because they 
do not have existence by virtue of themselves (per se) freed 
from (absolutum) the subject. But just as a substantial exist- 
ence ensues from form and matter when composited, so, too, 
an accidental existence ensues from accident and subject when 
the accident advenes to the subject. And therefore neither has 
the substantial form itself complete essence, nor has matter; 
because likewise in the definition of substantial form it is neces- 
sary to posit that of which it is the form, and so its definition 
is by virtue of the addition of something which is outside its 
genus, as is also the definition of the accidental form. Whence 
in the definition of soul body is posited by the naturalist who 
considers the soul only inasmuch as it is the form of a physical 
body. But nevertheless there is a difference between substantial 
form and accidental form because, just as substantial form does 
not have an absolute existence by virtue of itself without that 
to which it advenes, so neither does that to which it advenes, 
namely, matter. And therefore from the conjunction of both 
ensues that existence in which the thing subsists by virtue of 
itself (per se), and from them is effected a unity by virtue of 
itself (unum per se: a substantial unity) for the reason that 



a certain essence ensues from their conjunction. Whence the 
form, although considered in itself (in se) it does not possess 
the complete ratio of essence, is nevertheless part of a complete 
essence. But that to which the accident advenes is a being 
complete in itself (in se), subsisting in its own existence; 
which certain existence naturally precedes the accident which 
supervenes to it. And therefore the supervening accident, from 
its conjunction with that to which it advenes, does not cause 
that existence in which the thing subsists, through which the 
thing is a being by virtue of itself (ens per se), but it causes 
a certain secondary existence, without which the subsisting 
thing can be conceived, as the first can be conceived without 
the second. Whence from an accident and a subject is not ef- 
fected a unity by virtue of itself (unum per se: substantial 
unity), but a unity by virtue of accident (unum per accident: 
accidental unity). And therefore from their conjunction a cer- 
tain essence does not result, as from the conjunction of form 
with matter. For which reason an accident has neither the 
ratio of complete essence, nor is it a part of complete essence; 
but just as it is being in a certain respect (secundum quid), 
so also it has essence in a certain respect. 

But because that which is in the greatest degree and most 
truly asserted in any genus whatsoever is the cause of those 
things which are posterior in that genus, as for instance fire 
which is the extreme of hotness is the cause of heat in hot 
things, as is also said in the second book of the Metaphysics, 40 
therefore substance, which is first in the genus of being, hav- 
ing essence most truly and in the greatest degree, is necessarily 
the cause of accidents which participate the principle of 
being only secondarily and, as it were, in a certain respect 
(secundum quid). This however happens in diverse ways. For 
since the parts of a substance are matter and form, therefore 

40 Aristotle, Met. a, 993 b 24. 


certain accidents principally follow upon form, and others upon 
matter. Moreover, some form is found the existence of which 
does not depend on matter, as the intellective soul does not; 
but matter does not exist except by means of form. Whence in 
accidents which ensue from form there is something which has 
no communication with matter, as for instance to intellect, 
which is not by means of any corporeal organ, as the Philoso- 
pher proves in the third book of the De Animal But some of 
the things ensuing from the form have communication with 
matter, as for instance to sense, and things of this sort; but no 
accident ensues from matter without communication with 
form. Yet in these accidents which ensue from matter there 
is found a certain diversity. For certain accidents ensue from 
matter according to an order which they have to a special 
form, as for instance masculine and feminine in animals, the 
diversity of which is reduced to matter, as is said in the tenth 
book of the Metaphysics* 2 Whence the form of animal being 
removed, the accidents do not remain except equivocally. Cer- 
tain (accidents) ensue from matter according to an order 
which it has to a general form, and therefore, the special form 
being removed, they still remain (in the matter), as for in- 
stance blackness of skin is in the Ethiopian from a mixture of 
elements and not by reason of his soul, and therefore remains 
in him after death. And because each and every thing is in- 
dividuated from its matter and disposed in a genus or a species 
by virtue of its form, therefore accidents which ensue from 
matter are accidents of the individual, according to which in- 
dividuals of the same species differ from one another. But the 
accidents which ensue from form are proper passions of the 
genus or of the species, whence they are found in all things 
participating in the nature of the genus or of the species, as 

41 Aristotle, De An., 429 b 3. 

42 Aristotle, Met., I, 1058 b 21. 


for instance risibility in man ensues from the form, since 
a laugh arises from some apprehension in the soul of a 

One should know, too, that accidents are sometimes caused 
by the essential principles according to perfect act, as for in- 
stance heat in fire which is always hot in act; but at times 
(they are caused) only according to an aptitude, with comple- 
tion accruing to them from an exterior agent, as for instance 
transparency in the air which is completed by means of a lucid 
external body. And in such instances the aptitude is an in- 
separable accident, but the complement, which ensues to it 
from some principle which is outside the essence of the thing 
or which does not enter into its constitution, will be separable, 
as for instance to be moved and things of this sort, 

One should know therefore that in accidents genus, species 
and difference are taken in a mode other than that in which 
they are taken in substances. For since in substances there is 
effected from the substantial form and the matter a unity by 
virtue of itself {per se unum: a substantial unity), a certain 
nature resulting from their conjunction which is properly 
placed in the predicament (category) of substance, therefore in 
substances the concrete names which signify the composite are 
properly said to be in a genus, whether species or genus, as 
man or animal. However, neither form nor matter is in a 
predicament (category) in this mode except through reduction, 
as the former is said to be in a genus. But a substantial unity 
(unum per se) is not effected from an accident and its subject, 
and therefore no nature results from their conjunction to which 
the intention of genus or species can be attributed. Accordingly, 
the accidental names expressing a concretion, as for instance 
white man or musician, are not placed in a predicament (cate- 
gory), either as species or as genus, except by reduction, for 
they can be placed in a predicament only according to what is 


signified in the abstract, as for instance white or musical. And 
because accidents are not composed of matter and form, there- 
fore in them it is not possible to take the genus from the mat- 
ter and the difference from the form as in composite substances. 
But the genus must be taken primarily from its very mode of 
being inasmuch as being is asserted in diverse modes of the 
ten predicamental genera (categories) in accordance with the 
(order of) prior and posterior. So likewise it is called quantity 
according as it is the measure of substance and quality inas- 
much as it is said to be a disposition of substance, and likewise 
for the others (predicamental genera), as the Philosopher states 
in the fourth of the Metaphysics.** Indeed, difference in acci- 
dents is taken from the diversity of the principles from which 
they are caused. And because proper passions are caused from 
proper principles of the subject, therefore a subject is posited 
in their definition in place of difference, if they are defined 
abstractly (in absolutory according to which manner of defini- 
tion they are properly in a genus, as for instance it is said that 
snub-nosedness is a curvature of the nose. But the converap 
would hold if their definition were taken concretely. For thus 
the subject would be posited in their definition as their genus, 
seeing that they would then be defined as composite substances 
are, in which the ratio of the genus is taken from matter, as 
we say that a snub-nose is a curved nose. If one accident be the 
principle of another accident, the case is similar to the above, 
as for instance the principle of relation is action and passion 
and quantity; and therefore according to this the Philosopher 
divides relation in the Metaphysics** But since the proper 
principles of accidents are not always manifest, therefore some- 
times we take the difference of accidents from their effects, as 
condensing and dispersing are called differences of color, which 

48 Aristotle, Met., T, 1003 a 33 b 10. 
44 Aristotle, Met., A, 1020 b 26 ss. 


are caused from the abundance or paucity of light from which 
the different species of color result. 

Thus, therefore, it is clear in what mode essence is in sub- 
stances and in accidents, and in what mode it is in composite 
substances and in simple substances, and after what manner 
universal logical intentions are found in all these; with the ex- 
ception of the First which is the extreme of simplicity, and to 
which because of its simplicity neither the ratio of genus, nor 
of species, nor, consequently, definition applies. 

In which may the end and consummation of this discourse 
be. Amen. 


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Absolute: Freed or relatively freed from conditions of matter 
and hence from contingency. Abstracted from individu- 
ating conditions. 

Act and Potency: To be understood by the proportion of any 
two things to each other reciprocally. Act: being deter- 
mined. Potency: being determinable. Act and potency 
always import a disposition or the order of a change. 

Accident: That which does not have being in itself, but from 
another. (Ens in alio). Accidents are additions which ad- 
vene to a substance and bring it to a completion. 

Act of Being: Existence. An act, being determined, or the 
determined, or a terminated nature. 

Analysis: A grasp of organization by a scrutiny of relations and 
terms composing simple and complex substances, and 
completed by an apprehension of the relevant operation or 
operations involved, a. Platonic Analysis: Quality is elimi- 
nated, leaving quantity and relations. Platonists are apt to 
reify the relations and to invest them with autonomic 
energy, b. Aristotelian Analysis: Includes Platonic analysis 
and something in addition. Platonic analysis supplies the 
formal cause, but in addition there is the material and 
efficient cause, not to mention the final cause. Essences 
must needs be assigned to their existential operations or 
natures to become actual. Platonic essences are potentiali- 
ties or possibles, but in Aristotelian analysis the process in 
nature supplements the formal statement. 

Being: A transcendental predicate, (Ens), that which is, the 
actual nature of a thing or existence independent of the 
knowing mind. The principle of being (existence) and the 
principle of being primarily intelligible must be in some 
sense commensurate if being and truth are related. Modes 
of operating and knowing are said to follow upon the 



mode of being. Being, then, is the formal object of the 
intellect per se prime. 

Body and Soul, Union of: A substantial unity and not an ac- 
cidental unity. 

Composite: A concretion of matter and form or the advention 
of a form into a matter apt to receive it. 

Composition, Accidental: That which unites the accidents to 
the substance in which they inhere. 

Creature: A created thing. Each thing is and exists by its as- 
signed act and proper measure of perfection as such a 
mode of finite being in the infinite order derived from 

Disposition: Always imports an order of something which has 
parts. The arrangement of that which has parts as ordered 
in respect to place, to potency, or to quality; hence rela- 
tional order in one respect. See Act and Potency. 

Ens per se existent: A being existing by virtue of itself or its 
ordained nature. Since a being of this sort exists as a 
whole and in no wise as a part of another being it exists 
also in se. 

Essence: Is in relation to the act of existence a potentiality 
really distinct from existence, but actual in virtue of 
existence. It is that by virtue of which the intellect under- 
stands that which is necessarily and primarily the being of 
a nature or substance. Essence, then, is that by which a 
thing is necessarily and primarily as intelligible, or that 
by virtue of which a thing is constituted in a determinate 
degree of primarily intelligible being. By strict distinction 
an essence is a being of reason as distinguished from a 
being of nature, and hence an essence is the formal cause 
of knowing and is that in the active intellect by which a 
nature is known when it is known. In a realist or quasi- 
realist doctrine essence must express the real nature of 
being; consequently, it cannot be merely an arbitrary im- 
posed sign. 


Habit: Disposition to act in a fixed or ordained mode, or a 
fixed and determinate operation. An aptitude is a disposi- 
tion towards an order of operation, which has not become 
fixed and is therefore easily alterable. See above, Act and 
Potency and Disposition. 

Hierarchy: Aristotelian, a continuous order of differentiated 
beings having a beginning, a middle and an end. Those 
properties which remain unchanged in a scheme of sub- 
stances when the substances undergo alteration. Further, 
the relation of one grade of being or substances to others. 

Intelligence, Human: Last in the order of intelligences and 
first in the order of material forms. 

Intention: First Intention, the assimilated sensible in the sense; 
hence, a potential sign, or the potential sign as actual 
inasmuch as it signifies an individuated thing. Second 
Intention, Essence, or the formal equivalent by virtue of 
which that which is known is known in its necessary and 
primary being. 

Materia Signata: The lowest grade of matter endowed with 
merely an intrinsic aptitude for occupying certain relative 
dimensions of space. The basis of numerical multiplicity. 

Nature: The operation which anything is adapted or disposed 
to perform. Anything whatsoever possesses a constitutive 
principle by virtue of which it is that which it is and 
performs that which it performs its proper perfection 
or the aspect of its being which differentiates it. Nature is 
thought of as the opposite of essence in both the order 
of abstraction and the order of signation. Things must be 
apt to unite and possess unity in potency before they 
possess it in act. 

Objects (Things): Must be apt to unite and possess unity in 
potency before they possess it in act. In the natural order 
to be understood as natures known by means of essences. 

Operation, Order of: Action to Passion. 


Potency: Active, a power to operate; passive, a capacity to re- 
ceive. A power is to be understood as that which has a 
disposition or order to action. 

Privation: A negation in the subject. The absence of the formal 
principle required by the state in which the matter actually 
is. A privation : substance : : a negation : subject. 

Quality: A disposition of capacities or passive potencies, for the 
sake of an act; hence the order of operations according to 
which such a disposition of passive potencies become 

Quantity: The passive diffusion of matter in a three dimen- 
sional medium, and the first accident of material substance. 

Quiddity: An expression used as a neutral term between nature 
and essence. Usually understood however as equivalent to 
essence. It stands for the peculiar nature of the thing, not 
however as the thing is as individuated by conditions of 
matter but as it is necessarily and primarily according to 
its mode of being. 

Relation: A general sign for a possible modification between 
a and b, or the respect in which one thing stands to an- 
other thing, as of anything to something. Ad aliquid: the 
order of one thing to another. 

Signs, Order of: Genus, difference and property are all 
predicated necessarily; the distinctions among them rest 
not on the way in which they are asserted of things, but 
on the mode in which they signify the things signified by 
their subjects. Hence such signs are terms in the purely 
rational science of logic. 

Substance: Secondary, an analytic analogue (similitude of be- 
ing, i.e. a nature) as expressed by genus, species, property 
and difference in the rational order. Aristotle observes that 
primary substance (a nature) is to secondary substance 
(the formulae in the intellect) as species is to genus. 

Truth: A transcendental predicate conformity of essence to 


nature, or the adequation of the thing to the intellect and 

Unity, Substantial: Unum per se That which is one by virtue 
of its proper or intrinsic operation. It is opposed to unum 
per accidens or one by accident. A substantial unity is one 
by virtue of the operation by which it exists necessarily. 
An accidental unity is one merely by conjunction as the 
parts of an aggregate. Per se: brought into existence by 
a proper act, but indicating a measure of dependence from